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	$157.83	5.634%	$166.7221	$166.72	$166.70	$166.70
Purchase #2	$142.51	6.837%	$152.2534	$152.25	$152.25	$152.30
Purchase #3	$182.33	7.824%	$196.5955	$196.60	$196.60	$196.60
Purchase #4	$71.50	10.868%	$79.2706	$79.27	$79.25	$79.30
Purchase #5	$129.97	11.817%	$145.3286	$145.33	$145.35	$145.30
Purchase #6	$199.43	3.708%	$206.8249	$206.82	$206.80	$206.80
Purchase #7	$237.90	5.347%	$250.6205	$250.62	$250.60	$250.60
7 purchase totals =	$1,121.47		$1,197.6156	$1,197.61	$1,197.55	$1,197.60