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	$223.41	8.220%	$241.7743	$241.77	$241.75	$241.80
Purchase #2	$181.56	8.459%	$196.9182	$196.92	$196.90	$196.90
Purchase #3	$222.32	8.584%	$241.4039	$241.40	$241.40	$241.40
Purchase #4	$48.59	13.584%	$55.1905	$55.19	$55.20	$55.20
Purchase #5	$134.67	10.324%	$148.5733	$148.57	$148.55	$148.60
Purchase #6	$39.68	7.141%	$42.5135	$42.51	$42.50	$42.50
Purchase #7	$245.67	3.826%	$255.0693	$255.07	$255.05	$255.10
7 purchase totals =	$1,095.90		$1,181.4430	$1,181.43	$1,181.35	$1,181.50