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	$113.27	4.587%	$118.4657	$118.47	$118.45	$118.50
Purchase #2	$140.93	10.349%	$155.5148	$155.51	$155.50	$155.50
Purchase #3	$242.47	4.399%	$253.1363	$253.14	$253.15	$253.10
Purchase #4	$197.84	13.106%	$223.7689	$223.77	$223.75	$223.80
Purchase #5	$222.33	9.367%	$243.1557	$243.16	$243.15	$243.20
Purchase #6	$45.48	11.430%	$50.6784	$50.68	$50.70	$50.70
Purchase #7	$5.90	4.164%	$6.1457	$6.15	$6.15	$6.10
7 purchase totals =	$968.22		$1,050.8655	$1,050.88	$1,050.85	$1,050.90