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	$122.77	5.511%	$129.5359	$129.54	$129.55	$129.50
Purchase #2	$210.80	5.671%	$222.7545	$222.75	$222.75	$222.80
Purchase #3	$245.55	12.645%	$276.5998	$276.60	$276.60	$276.60
Purchase #4	$100.91	8.779%	$109.7689	$109.77	$109.75	$109.80
Purchase #5	$66.81	8.768%	$72.6679	$72.67	$72.65	$72.70
Purchase #6	$244.77	12.678%	$275.8019	$275.80	$275.80	$275.80
Purchase #7	$33.58	12.784%	$37.8729	$37.87	$37.85	$37.90
7 purchase totals =	$1,025.19		$1,125.0018	$1,125.00	$1,124.95	$1,125.10