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	$125.61	8.632%	$136.4527	$136.45	$136.45	$136.50
Purchase #2	$35.35	6.766%	$37.7418	$37.74	$37.75	$37.70
Purchase #3	$134.85	10.168%	$148.5615	$148.56	$148.55	$148.60
Purchase #4	$189.48	11.846%	$211.9258	$211.93	$211.95	$211.90
Purchase #5	$78.55	7.587%	$84.5096	$84.51	$84.50	$84.50
Purchase #6	$92.33	7.710%	$99.4486	$99.45	$99.45	$99.40
Purchase #7	$10.79	6.364%	$11.4767	$11.48	$11.50	$11.50
7 purchase totals =	$666.96		$730.1167	$730.12	$730.15	$730.10