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	$96.73	7.677%	$104.156	$104.16	$104.15	$104.20
Purchase #2	$179.38	6.233%	$190.5608	$190.56	$190.55	$190.60
Purchase #3	$109.25	11.493%	$121.8061	$121.81	$121.80	$121.80
Purchase #4	$121.40	12.755%	$136.8846	$136.88	$136.90	$136.90
Purchase #5	$247.31	9.318%	$270.3543	$270.35	$270.35	$270.40
Purchase #6	$93.82	6.642%	$100.0515	$100.05	$100.05	$100.10
Purchase #7	$123.94	10.157%	$136.5286	$136.53	$136.55	$136.50
7 purchase totals =	$971.83		$1,060.3419	$1,060.34	$1,060.35	$1,060.50