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	$137.87	7.221%	$147.8256	$147.83	$147.85	$147.80
Purchase #2	$93.80	12.370%	$105.4031	$105.40	$105.40	$105.40
Purchase #3	$83.91	6.168%	$89.0856	$89.09	$89.10	$89.10
Purchase #4	$34.33	8.781%	$37.3445	$37.34	$37.35	$37.30
Purchase #5	$103.31	7.621%	$111.1833	$111.18	$111.20	$111.20
Purchase #6	$137.72	11.376%	$153.387	$153.39	$153.40	$153.40
Purchase #7	$104.91	4.532%	$109.6645	$109.66	$109.65	$109.70
7 purchase totals =	$695.85		$753.8936	$753.89	$753.95	$753.90