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	$96.96	12.468%	$109.049	$109.05	$109.05	$109.00
Purchase #2	$211.36	4.837%	$221.5835	$221.58	$221.60	$221.60
Purchase #3	$34.28	9.192%	$37.431	$37.43	$37.45	$37.40
Purchase #4	$89.39	7.763%	$96.3293	$96.33	$96.35	$96.30
Purchase #5	$231.42	6.873%	$247.3255	$247.33	$247.35	$247.30
Purchase #6	$141.37	8.535%	$153.4359	$153.44	$153.45	$153.40
Purchase #7	$133.30	7.628%	$143.4681	$143.47	$143.45	$143.50
7 purchase totals =	$938.08		$1,008.6223	$1,008.63	$1,008.70	$1,008.50