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	$98.88	12.524%	$111.2637	$111.26	$111.25	$111.30
Purchase #2	$30.43	12.265%	$34.1622	$34.16	$34.15	$34.20
Purchase #3	$199.93	11.754%	$223.4298	$223.43	$223.45	$223.40
Purchase #4	$7.27	8.495%	$7.8876	$7.89	$7.90	$7.90
Purchase #5	$45.39	5.641%	$47.9504	$47.95	$47.95	$48.00
Purchase #6	$30.64	12.517%	$34.4752	$34.48	$34.50	$34.50
Purchase #7	$234.59	9.621%	$257.1599	$257.16	$257.15	$257.20
7 purchase totals =	$647.13		$716.3288	$716.33	$716.35	$716.50