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	$43.46	11.684%	$48.5379	$48.54	$48.55	$48.50
Purchase #2	$177.33	4.732%	$185.7213	$185.72	$185.70	$185.70
Purchase #3	$218.40	7.582%	$234.9591	$234.96	$234.95	$235.00
Purchase #4	$60.78	3.160%	$62.7006	$62.70	$62.70	$62.70
Purchase #5	$82.40	12.562%	$92.7511	$92.75	$92.75	$92.80
Purchase #6	$81.38	12.296%	$91.3865	$91.39	$91.40	$91.40
Purchase #7	$35.51	5.606%	$37.5007	$37.50	$37.50	$37.50
7 purchase totals =	$699.26		$753.5572	$753.56	$753.55	$753.60