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	$175.29	9.790%	$192.4509	$192.45	$192.45	$192.50
Purchase #2	$84.50	4.337%	$88.1648	$88.16	$88.15	$88.20
Purchase #3	$179.72	11.791%	$200.9108	$200.91	$200.90	$200.90
Purchase #4	$102.28	12.163%	$114.7203	$114.72	$114.70	$114.70
Purchase #5	$42.48	12.635%	$47.8473	$47.85	$47.85	$47.80
Purchase #6	$216.67	8.198%	$234.4326	$234.43	$234.45	$234.40
Purchase #7	$129.60	8.828%	$141.0411	$141.04	$141.05	$141.00
7 purchase totals =	$930.54		$1,019.5678	$1,019.56	$1,019.55	$1,019.50