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	$174.39	13.668%	$198.2256	$198.23	$198.25	$198.20
Purchase #2	$232.56	9.869%	$255.5113	$255.51	$255.50	$255.50
Purchase #3	$194.82	8.773%	$211.9116	$211.91	$211.90	$211.90
Purchase #4	$238.37	7.137%	$255.3825	$255.38	$255.40	$255.40
Purchase #5	$103.89	6.362%	$110.4995	$110.50	$110.50	$110.50
Purchase #6	$77.89	4.660%	$81.5197	$81.52	$81.50	$81.50
Purchase #7	$233.44	9.198%	$254.9118	$254.91	$254.90	$254.90
7 purchase totals =	$1,255.36		$1,367.9620	$1,367.96	$1,367.95	$1,367.90