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	$54.50	4.791%	$57.1111	$57.11	$57.10	$57.10
Purchase #2	$235.73	3.263%	$243.4219	$243.42	$243.40	$243.40
Purchase #3	$137.34	8.128%	$148.503	$148.50	$148.50	$148.50
Purchase #4	$95.74	7.431%	$102.8544	$102.85	$102.85	$102.90
Purchase #5	$100.53	3.714%	$104.2637	$104.26	$104.25	$104.30
Purchase #6	$244.32	12.437%	$274.7061	$274.71	$274.70	$274.70
Purchase #7	$78.57	9.244%	$85.833	$85.83	$85.85	$85.80
7 purchase totals =	$946.73		$1,016.6932	$1,016.68	$1,016.65	$1,016.70