Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.59	11.486%	$210.2514	$210.25	$210.25	$210.30
Purchase #2	$169.44	11.444%	$188.8307	$188.83	$188.85	$188.80
Purchase #3	$90.25	13.392%	$102.3363	$102.34	$102.35	$102.30
Purchase #4	$178.81	3.363%	$184.8234	$184.82	$184.80	$184.80
Purchase #5	$247.50	10.515%	$273.5246	$273.52	$273.50	$273.50
Purchase #6	$164.53	13.401%	$186.5787	$186.58	$186.60	$186.60
Purchase #7	$121.25	10.538%	$134.0273	$134.03	$134.05	$134.00
7 purchase totals =	$1,160.37		$1,280.3724	$1,280.37	$1,280.40	$1,280.30