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	$218.67	6.869%	$233.6904	$233.69	$233.70	$233.70
Purchase #2	$216.82	11.712%	$242.214	$242.21	$242.20	$242.20
Purchase #3	$51.98	3.560%	$53.8305	$53.83	$53.85	$53.80
Purchase #4	$123.74	7.716%	$133.2878	$133.29	$133.30	$133.30
Purchase #5	$200.45	7.760%	$216.0049	$216.00	$216.00	$216.00
Purchase #6	$178.34	11.147%	$198.2196	$198.22	$198.20	$198.20
Purchase #7	$52.73	12.777%	$59.4673	$59.47	$59.45	$59.50
7 purchase totals =	$1,042.73		$1,136.7145	$1,136.71	$1,136.70	$1,136.70