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	$229.81	4.748%	$240.7214	$240.72	$240.70	$240.70
Purchase #2	$223.43	4.591%	$233.6877	$233.69	$233.70	$233.70
Purchase #3	$157.47	9.382%	$172.2438	$172.24	$172.25	$172.20
Purchase #4	$31.66	11.650%	$35.3484	$35.35	$35.35	$35.30
Purchase #5	$74.54	9.661%	$81.7413	$81.74	$81.75	$81.70
Purchase #6	$133.81	4.137%	$139.3457	$139.35	$139.35	$139.30
Purchase #7	$96.81	8.485%	$105.0243	$105.02	$105.00	$105.00
7 purchase totals =	$947.53		$1,008.1126	$1,008.11	$1,008.10	$1,007.90