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	$106.55	12.341%	$119.6993	$119.70	$119.70	$119.70
Purchase #2	$145.69	7.568%	$156.7158	$156.72	$156.70	$156.70
Purchase #3	$237.42	5.228%	$249.8323	$249.83	$249.85	$249.80
Purchase #4	$86.88	4.281%	$90.5993	$90.60	$90.60	$90.60
Purchase #5	$205.53	7.651%	$221.2551	$221.26	$221.25	$221.30
Purchase #6	$111.94	11.445%	$124.7515	$124.75	$124.75	$124.80
Purchase #7	$35.64	11.398%	$39.7022	$39.70	$39.70	$39.70
7 purchase totals =	$929.65		$1,002.5555	$1,002.56	$1,002.55	$1,002.60