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	$227.67	9.312%	$248.8706	$248.87	$248.85	$248.90
Purchase #2	$99.98	11.622%	$111.5997	$111.60	$111.60	$111.60
Purchase #3	$168.79	8.204%	$182.6375	$182.64	$182.65	$182.60
Purchase #4	$112.53	11.735%	$125.7354	$125.74	$125.75	$125.70
Purchase #5	$184.59	6.543%	$196.6677	$196.67	$196.65	$196.70
Purchase #6	$224.59	9.729%	$246.4404	$246.44	$246.45	$246.40
Purchase #7	$62.46	6.152%	$66.3025	$66.30	$66.30	$66.30
7 purchase totals =	$1,080.61		$1,178.2538	$1,178.26	$1,178.25	$1,178.20