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	$60.87	11.158%	$67.6619	$67.66	$67.65	$67.70
Purchase #2	$61.79	7.776%	$66.5948	$66.59	$66.60	$66.60
Purchase #3	$98.80	4.586%	$103.331	$103.33	$103.35	$103.30
Purchase #4	$205.33	11.106%	$228.1339	$228.13	$228.15	$228.10
Purchase #5	$147.65	11.417%	$164.5072	$164.51	$164.50	$164.50
Purchase #6	$89.69	5.471%	$94.5969	$94.60	$94.60	$94.60
Purchase #7	$32.33	13.381%	$36.6561	$36.66	$36.65	$36.70
7 purchase totals =	$696.46		$761.4818	$761.48	$761.50	$761.50