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	$173.90	10.578%	$192.2951	$192.30	$192.30	$192.30
Purchase #2	$48.84	9.109%	$53.2888	$53.29	$53.30	$53.30
Purchase #3	$191.35	4.179%	$199.3465	$199.35	$199.35	$199.30
Purchase #4	$26.78	9.561%	$29.3404	$29.34	$29.35	$29.30
Purchase #5	$237.94	13.141%	$269.2077	$269.21	$269.20	$269.20
Purchase #6	$172.33	10.534%	$190.4832	$190.48	$190.50	$190.50
Purchase #7	$100.64	11.760%	$112.4753	$112.48	$112.50	$112.50
7 purchase totals =	$951.78		$1,046.4370	$1,046.45	$1,046.50	$1,046.40