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	$45.26	6.729%	$48.3055	$48.31	$48.30	$48.30
Purchase #2	$18.27	8.700%	$19.8595	$19.86	$19.85	$19.90
Purchase #3	$203.50	9.515%	$222.863	$222.86	$222.85	$222.90
Purchase #4	$105.97	13.291%	$120.0545	$120.05	$120.05	$120.10
Purchase #5	$149.96	3.431%	$155.1051	$155.11	$155.10	$155.10
Purchase #6	$33.80	13.204%	$38.263	$38.26	$38.25	$38.30
Purchase #7	$70.90	4.208%	$73.8835	$73.88	$73.90	$73.90
7 purchase totals =	$627.66		$678.3341	$678.33	$678.30	$678.50