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	$33.49	12.516%	$37.6816	$37.68	$37.70	$37.70
Purchase #2	$151.37	6.147%	$160.6747	$160.67	$160.65	$160.70
Purchase #3	$31.69	5.115%	$33.3109	$33.31	$33.30	$33.30
Purchase #4	$41.72	10.429%	$46.071	$46.07	$46.05	$46.10
Purchase #5	$244.89	11.590%	$273.2728	$273.27	$273.25	$273.30
Purchase #6	$8.97	7.290%	$9.6239	$9.62	$9.60	$9.60
Purchase #7	$36.58	11.711%	$40.8639	$40.86	$40.85	$40.90
7 purchase totals =	$548.71		$601.4988	$601.48	$601.40	$601.60