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	$218.98	7.152%	$234.6414	$234.64	$234.65	$234.60
Purchase #2	$90.55	12.371%	$101.7519	$101.75	$101.75	$101.80
Purchase #3	$172.53	13.693%	$196.1545	$196.15	$196.15	$196.20
Purchase #4	$141.96	5.380%	$149.5974	$149.60	$149.60	$149.60
Purchase #5	$229.51	9.219%	$250.6685	$250.67	$250.65	$250.70
Purchase #6	$30.70	7.425%	$32.9795	$32.98	$33.00	$33.00
Purchase #7	$85.52	3.539%	$88.5466	$88.55	$88.55	$88.50
7 purchase totals =	$969.75		$1,054.3398	$1,054.34	$1,054.35	$1,054.40