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	$236.76	7.725%	$255.0497	$255.05	$255.05	$255.00
Purchase #2	$192.38	5.762%	$203.4649	$203.46	$203.45	$203.50
Purchase #3	$165.86	9.193%	$181.1075	$181.11	$181.10	$181.10
Purchase #4	$120.29	8.591%	$130.6241	$130.62	$130.60	$130.60
Purchase #5	$45.71	3.776%	$47.436	$47.44	$47.45	$47.40
Purchase #6	$88.78	11.790%	$99.2472	$99.25	$99.25	$99.20
Purchase #7	$55.25	6.707%	$58.9556	$58.96	$58.95	$59.00
7 purchase totals =	$905.03		$975.8850	$975.89	$975.85	$975.80