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	$43.53	3.191%	$44.919	$44.92	$44.90	$44.90
Purchase #2	$62.96	3.412%	$65.1082	$65.11	$65.10	$65.10
Purchase #3	$246.32	11.623%	$274.9498	$274.95	$274.95	$274.90
Purchase #4	$79.50	5.520%	$83.8884	$83.89	$83.90	$83.90
Purchase #5	$185.42	12.551%	$208.6921	$208.69	$208.70	$208.70
Purchase #6	$115.88	13.203%	$131.1796	$131.18	$131.20	$131.20
Purchase #7	$34.99	8.155%	$37.8434	$37.84	$37.85	$37.80
7 purchase totals =	$768.60		$846.5805	$846.58	$846.60	$846.50