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	$192.53	8.785%	$209.4438	$209.44	$209.45	$209.40
Purchase #2	$148.44	7.476%	$159.5374	$159.54	$159.55	$159.50
Purchase #3	$222.42	12.646%	$250.5472	$250.55	$250.55	$250.50
Purchase #4	$123.83	12.866%	$139.762	$139.76	$139.75	$139.80
Purchase #5	$105.85	5.532%	$111.7056	$111.71	$111.70	$111.70
Purchase #6	$97.70	9.398%	$106.8818	$106.88	$106.90	$106.90
Purchase #7	$71.42	11.486%	$79.6233	$79.62	$79.60	$79.60
7 purchase totals =	$962.19		$1,057.5011	$1,057.50	$1,057.50	$1,057.40