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	$206.89	7.344%	$222.084	$222.08	$222.10	$222.10
Purchase #2	$40.74	12.602%	$45.8741	$45.87	$45.85	$45.90
Purchase #3	$56.48	8.190%	$61.1057	$61.11	$61.10	$61.10
Purchase #4	$138.63	3.401%	$143.3448	$143.34	$143.35	$143.30
Purchase #5	$207.76	10.233%	$229.0201	$229.02	$229.00	$229.00
Purchase #6	$68.34	11.313%	$76.0713	$76.07	$76.05	$76.10
Purchase #7	$108.91	13.751%	$123.8862	$123.89	$123.90	$123.90
7 purchase totals =	$827.75		$901.3862	$901.38	$901.35	$901.40