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	$93.32	12.689%	$105.1614	$105.16	$105.15	$105.20
Purchase #2	$41.54	7.837%	$44.7955	$44.80	$44.80	$44.80
Purchase #3	$12.34	11.651%	$13.7777	$13.78	$13.80	$13.80
Purchase #4	$158.79	8.570%	$172.3983	$172.40	$172.40	$172.40
Purchase #5	$120.30	9.578%	$131.8223	$131.82	$131.80	$131.80
Purchase #6	$171.51	11.761%	$191.6813	$191.68	$191.70	$191.70
Purchase #7	$240.82	9.319%	$263.262	$263.26	$263.25	$263.30
7 purchase totals =	$838.62		$922.8985	$922.90	$922.90	$923.00