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	$229.96	10.223%	$253.4688	$253.47	$253.45	$253.50
Purchase #2	$121.69	5.217%	$128.0386	$128.04	$128.05	$128.00
Purchase #3	$123.33	10.599%	$136.4017	$136.40	$136.40	$136.40
Purchase #4	$149.33	11.847%	$167.0211	$167.02	$167.00	$167.00
Purchase #5	$209.96	13.575%	$238.4621	$238.46	$238.45	$238.50
Purchase #6	$143.74	13.255%	$162.7927	$162.79	$162.80	$162.80
Purchase #7	$85.81	10.139%	$94.5103	$94.51	$94.50	$94.50
7 purchase totals =	$1,063.82		$1,180.6953	$1,180.69	$1,180.65	$1,180.70