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	$209.57	9.455%	$229.3848	$229.38	$229.40	$229.40
Purchase #2	$250.77	4.344%	$261.6634	$261.66	$261.65	$261.70
Purchase #3	$105.57	5.796%	$111.6888	$111.69	$111.70	$111.70
Purchase #4	$222.46	12.644%	$250.5878	$250.59	$250.60	$250.60
Purchase #5	$50.36	3.555%	$52.1503	$52.15	$52.15	$52.20
Purchase #6	$234.58	8.518%	$254.5615	$254.56	$254.55	$254.60
Purchase #7	$225.53	3.443%	$233.295	$233.30	$233.30	$233.30
7 purchase totals =	$1,298.84		$1,393.3316	$1,393.33	$1,393.35	$1,393.50