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	$100.76	7.567%	$108.3845	$108.38	$108.40	$108.40
Purchase #2	$141.58	11.731%	$158.1887	$158.19	$158.20	$158.20
Purchase #3	$185.80	7.611%	$199.9412	$199.94	$199.95	$199.90
Purchase #4	$35.57	11.274%	$39.5802	$39.58	$39.60	$39.60
Purchase #5	$248.54	10.700%	$275.1338	$275.13	$275.15	$275.10
Purchase #6	$229.77	12.455%	$258.3879	$258.39	$258.40	$258.40
Purchase #7	$109.59	7.606%	$117.9254	$117.93	$117.95	$117.90
7 purchase totals =	$1,051.61		$1,157.5417	$1,157.54	$1,157.65	$1,157.50