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	$243.37	6.232%	$258.5368	$258.54	$258.55	$258.50
Purchase #2	$233.75	3.272%	$241.3983	$241.40	$241.40	$241.40
Purchase #3	$61.78	7.660%	$66.5123	$66.51	$66.50	$66.50
Purchase #4	$68.29	10.455%	$75.4297	$75.43	$75.45	$75.40
Purchase #5	$234.81	6.562%	$250.2182	$250.22	$250.20	$250.20
Purchase #6	$187.71	4.500%	$196.157	$196.16	$196.15	$196.20
Purchase #7	$62.58	12.616%	$70.4751	$70.48	$70.50	$70.50
7 purchase totals =	$1,092.29		$1,158.7274	$1,158.74	$1,158.75	$1,158.70