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	$147.46	6.432%	$156.9446	$156.94	$156.95	$156.90
Purchase #2	$111.67	8.402%	$121.0525	$121.05	$121.05	$121.10
Purchase #3	$148.44	10.799%	$164.47	$164.47	$164.45	$164.50
Purchase #4	$58.82	4.714%	$61.5928	$61.59	$61.60	$61.60
Purchase #5	$138.84	5.175%	$146.025	$146.03	$146.05	$146.00
Purchase #6	$175.85	13.596%	$199.7586	$199.76	$199.75	$199.80
Purchase #7	$197.61	13.628%	$224.5403	$224.54	$224.55	$224.50
7 purchase totals =	$978.69		$1,074.3838	$1,074.38	$1,074.40	$1,074.40