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	$177.28	7.802%	$191.1114	$191.11	$191.10	$191.10
Purchase #2	$121.58	3.305%	$125.5982	$125.60	$125.60	$125.60
Purchase #3	$50.68	4.649%	$53.0361	$53.04	$53.05	$53.00
Purchase #4	$39.89	6.519%	$42.4904	$42.49	$42.50	$42.50
Purchase #5	$99.34	12.477%	$111.7347	$111.73	$111.75	$111.70
Purchase #6	$205.96	12.527%	$231.7606	$231.76	$231.75	$231.80
Purchase #7	$168.63	4.140%	$175.6113	$175.61	$175.60	$175.60
7 purchase totals =	$863.36		$931.3427	$931.34	$931.35	$931.30