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	$169.88	12.455%	$191.0386	$191.04	$191.05	$191.00
Purchase #2	$58.27	11.636%	$65.0503	$65.05	$65.05	$65.10
Purchase #3	$157.93	6.301%	$167.8812	$167.88	$167.90	$167.90
Purchase #4	$16.88	10.117%	$18.5877	$18.59	$18.60	$18.60
Purchase #5	$91.89	4.102%	$95.6593	$95.66	$95.65	$95.70
Purchase #6	$131.41	9.595%	$144.0188	$144.02	$144.00	$144.00
Purchase #7	$218.47	13.865%	$248.7609	$248.76	$248.75	$248.80
7 purchase totals =	$844.73		$930.9968	$931.00	$931.00	$931.10