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	$146.53	9.559%	$160.5368	$160.54	$160.55	$160.50
Purchase #2	$165.70	10.338%	$182.8301	$182.83	$182.85	$182.80
Purchase #3	$110.62	11.621%	$123.4752	$123.48	$123.50	$123.50
Purchase #4	$235.25	6.598%	$250.7718	$250.77	$250.75	$250.80
Purchase #5	$37.86	10.361%	$41.7827	$41.78	$41.80	$41.80
Purchase #6	$54.36	11.709%	$60.725	$60.73	$60.75	$60.70
Purchase #7	$166.35	11.257%	$185.076	$185.08	$185.10	$185.10
7 purchase totals =	$916.67		$1,005.1976	$1,005.21	$1,005.30	$1,005.20