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	$204.90	4.734%	$214.6	$214.60	$214.60	$214.60
Purchase #2	$120.35	5.812%	$127.3447	$127.34	$127.35	$127.30
Purchase #3	$99.89	11.255%	$111.1326	$111.13	$111.15	$111.10
Purchase #4	$82.70	8.298%	$89.5624	$89.56	$89.55	$89.60
Purchase #5	$190.86	13.280%	$216.2062	$216.21	$216.20	$216.20
Purchase #6	$185.54	4.214%	$193.3587	$193.36	$193.35	$193.40
Purchase #7	$58.41	3.197%	$60.2774	$60.28	$60.30	$60.30
7 purchase totals =	$942.65		$1,012.4820	$1,012.48	$1,012.50	$1,012.50