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	$67.44	7.642%	$72.5938	$72.59	$72.60	$72.60
Purchase #2	$128.34	10.231%	$141.4705	$141.47	$141.45	$141.50
Purchase #3	$78.78	12.193%	$88.3856	$88.39	$88.40	$88.40
Purchase #4	$241.90	3.741%	$250.9495	$250.95	$250.95	$250.90
Purchase #5	$55.69	13.841%	$63.3981	$63.40	$63.40	$63.40
Purchase #6	$46.30	12.550%	$52.1107	$52.11	$52.10	$52.10
Purchase #7	$85.87	7.480%	$92.2931	$92.29	$92.30	$92.30
7 purchase totals =	$704.32		$761.2013	$761.20	$761.20	$761.20