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	$215.33	12.671%	$242.6145	$242.61	$242.60	$242.60
Purchase #2	$153.96	12.229%	$172.7878	$172.79	$172.80	$172.80
Purchase #3	$43.76	6.344%	$46.5361	$46.54	$46.55	$46.50
Purchase #4	$179.98	3.125%	$185.6044	$185.60	$185.60	$185.60
Purchase #5	$204.54	6.274%	$217.3728	$217.37	$217.35	$217.40
Purchase #6	$224.87	11.352%	$250.3972	$250.40	$250.40	$250.40
Purchase #7	$92.40	3.546%	$95.6765	$95.68	$95.70	$95.70
7 purchase totals =	$1,114.84		$1,210.9893	$1,210.99	$1,211.00	$1,211.00