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	$113.65	9.581%	$124.5388	$124.54	$124.55	$124.50
Purchase #2	$212.61	4.624%	$222.4411	$222.44	$222.45	$222.40
Purchase #3	$241.83	10.384%	$266.9416	$266.94	$266.95	$266.90
Purchase #4	$131.45	13.322%	$148.9618	$148.96	$148.95	$149.00
Purchase #5	$65.78	9.315%	$71.9074	$71.91	$71.90	$71.90
Purchase #6	$149.93	11.211%	$166.7387	$166.74	$166.75	$166.70
Purchase #7	$17.30	11.871%	$19.3537	$19.35	$19.35	$19.40
7 purchase totals =	$932.55		$1,020.8831	$1,020.88	$1,020.90	$1,020.80