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	$182.25	4.543%	$190.5296	$190.53	$190.55	$190.50
Purchase #2	$59.83	5.169%	$62.9226	$62.92	$62.90	$62.90
Purchase #3	$245.46	12.380%	$275.8479	$275.85	$275.85	$275.80
Purchase #4	$154.64	4.136%	$161.0359	$161.04	$161.05	$161.00
Purchase #5	$237.96	6.374%	$253.1276	$253.13	$253.15	$253.10
Purchase #6	$103.59	7.265%	$111.1158	$111.12	$111.10	$111.10
Purchase #7	$238.73	8.618%	$259.3038	$259.30	$259.30	$259.30
7 purchase totals =	$1,222.46		$1,313.8832	$1,313.89	$1,313.90	$1,313.70