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	$92.41	13.540%	$104.9223	$104.92	$104.90	$104.90
Purchase #2	$155.28	10.680%	$171.8639	$171.86	$171.85	$171.90
Purchase #3	$99.55	4.770%	$104.2985	$104.30	$104.30	$104.30
Purchase #4	$174.78	5.227%	$183.9158	$183.92	$183.90	$183.90
Purchase #5	$65.85	9.195%	$71.9049	$71.90	$71.90	$71.90
Purchase #6	$68.37	11.191%	$76.0213	$76.02	$76.00	$76.00
Purchase #7	$30.41	8.427%	$32.9727	$32.97	$32.95	$33.00
7 purchase totals =	$686.65		$745.8994	$745.89	$745.80	$745.90