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	$59.85	11.173%	$66.537	$66.54	$66.55	$66.50
Purchase #2	$83.62	12.732%	$94.2665	$94.27	$94.25	$94.30
Purchase #3	$183.63	11.631%	$204.988	$204.99	$205.00	$205.00
Purchase #4	$245.63	4.250%	$256.0693	$256.07	$256.05	$256.10
Purchase #5	$204.63	9.738%	$224.5569	$224.56	$224.55	$224.60
Purchase #6	$37.96	11.468%	$42.3133	$42.31	$42.30	$42.30
Purchase #7	$161.41	6.626%	$172.105	$172.11	$172.10	$172.10
7 purchase totals =	$976.73		$1,060.8360	$1,060.85	$1,060.80	$1,060.90