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	$226.43	3.837%	$235.1181	$235.12	$235.10	$235.10
Purchase #2	$104.72	6.356%	$111.376	$111.38	$111.40	$111.40
Purchase #3	$202.77	11.326%	$225.7357	$225.74	$225.75	$225.70
Purchase #4	$125.26	11.315%	$139.4332	$139.43	$139.45	$139.40
Purchase #5	$184.66	5.335%	$194.5116	$194.51	$194.50	$194.50
Purchase #6	$165.49	11.123%	$183.8975	$183.90	$183.90	$183.90
Purchase #7	$219.29	11.222%	$243.8987	$243.90	$243.90	$243.90
7 purchase totals =	$1,228.62		$1,333.9708	$1,333.98	$1,334.00	$1,333.90