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	$125.74	12.104%	$140.9596	$140.96	$140.95	$141.00
Purchase #2	$129.59	6.232%	$137.666	$137.67	$137.65	$137.70
Purchase #3	$231.67	9.371%	$253.3798	$253.38	$253.40	$253.40
Purchase #4	$105.39	13.454%	$119.5692	$119.57	$119.55	$119.60
Purchase #5	$153.47	3.179%	$158.3488	$158.35	$158.35	$158.30
Purchase #6	$47.76	10.152%	$52.6086	$52.61	$52.60	$52.60
Purchase #7	$224.38	3.355%	$231.9079	$231.91	$231.90	$231.90
7 purchase totals =	$1,018.00		$1,094.4399	$1,094.45	$1,094.40	$1,094.50