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	$57.72	3.634%	$59.8175	$59.82	$59.80	$59.80
Purchase #2	$238.52	10.167%	$262.7703	$262.77	$262.75	$262.80
Purchase #3	$240.34	11.409%	$267.7604	$267.76	$267.75	$267.80
Purchase #4	$248.37	8.546%	$269.5957	$269.60	$269.60	$269.60
Purchase #5	$190.87	8.379%	$206.863	$206.86	$206.85	$206.90
Purchase #6	$189.44	3.562%	$196.1879	$196.19	$196.20	$196.20
Purchase #7	$109.56	8.303%	$118.6568	$118.66	$118.65	$118.70
7 purchase totals =	$1,274.82		$1,381.6516	$1,381.66	$1,381.60	$1,381.80