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	$137.41	9.264%	$150.1397	$150.14	$150.15	$150.10
Purchase #2	$145.36	4.667%	$152.144	$152.14	$152.15	$152.10
Purchase #3	$216.71	9.621%	$237.5597	$237.56	$237.55	$237.60
Purchase #4	$91.66	4.187%	$95.4978	$95.50	$95.50	$95.50
Purchase #5	$90.86	5.384%	$95.7519	$95.75	$95.75	$95.80
Purchase #6	$157.63	7.281%	$169.107	$169.11	$169.10	$169.10
Purchase #7	$29.83	4.487%	$31.1685	$31.17	$31.15	$31.20
7 purchase totals =	$869.46		$931.3686	$931.37	$931.35	$931.40