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	$187.70	12.287%	$210.7627	$210.76	$210.75	$210.80
Purchase #2	$110.88	3.838%	$115.1356	$115.14	$115.15	$115.10
Purchase #3	$79.59	13.800%	$90.5734	$90.57	$90.55	$90.60
Purchase #4	$32.77	12.743%	$36.9459	$36.95	$36.95	$36.90
Purchase #5	$243.61	6.568%	$259.6103	$259.61	$259.60	$259.60
Purchase #6	$57.72	11.325%	$64.2568	$64.26	$64.25	$64.30
Purchase #7	$250.77	13.455%	$284.5111	$284.51	$284.50	$284.50
7 purchase totals =	$963.04		$1,061.7958	$1,061.80	$1,061.75	$1,061.80