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	$117.25	9.276%	$128.1261	$128.13	$128.15	$128.10
Purchase #2	$237.94	7.411%	$255.5737	$255.57	$255.55	$255.60
Purchase #3	$197.57	3.738%	$204.9552	$204.96	$204.95	$205.00
Purchase #4	$135.28	11.292%	$150.5558	$150.56	$150.55	$150.60
Purchase #5	$121.34	3.568%	$125.6694	$125.67	$125.65	$125.70
Purchase #6	$145.96	13.366%	$165.469	$165.47	$165.45	$165.50
Purchase #7	$52.78	4.650%	$55.2343	$55.23	$55.25	$55.20
7 purchase totals =	$1,008.12		$1,085.5835	$1,085.59	$1,085.55	$1,085.70