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	$94.51	3.848%	$98.1467	$98.15	$98.15	$98.10
Purchase #2	$30.38	7.118%	$32.5424	$32.54	$32.55	$32.50
Purchase #3	$153.97	5.653%	$162.6739	$162.67	$162.65	$162.70
Purchase #4	$57.89	13.809%	$65.884	$65.88	$65.90	$65.90
Purchase #5	$126.31	8.610%	$137.1853	$137.19	$137.20	$137.20
Purchase #6	$226.90	9.375%	$248.1719	$248.17	$248.15	$248.20
Purchase #7	$212.52	7.243%	$227.9128	$227.91	$227.90	$227.90
7 purchase totals =	$902.48		$972.5170	$972.51	$972.50	$972.50