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	$194.91	13.441%	$221.1079	$221.11	$221.10	$221.10
Purchase #2	$72.72	10.199%	$80.1367	$80.14	$80.15	$80.10
Purchase #3	$211.80	5.466%	$223.377	$223.38	$223.40	$223.40
Purchase #4	$134.43	4.530%	$140.5197	$140.52	$140.50	$140.50
Purchase #5	$20.37	7.225%	$21.8417	$21.84	$21.85	$21.80
Purchase #6	$234.38	5.499%	$247.2686	$247.27	$247.25	$247.30
Purchase #7	$192.45	13.732%	$218.8772	$218.88	$218.90	$218.90
7 purchase totals =	$1,061.06		$1,153.1288	$1,153.14	$1,153.15	$1,153.10