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	$176.57	3.187%	$182.1973	$182.20	$182.20	$182.20
Purchase #2	$141.86	6.650%	$151.2937	$151.29	$151.30	$151.30
Purchase #3	$193.66	3.342%	$200.1321	$200.13	$200.15	$200.10
Purchase #4	$73.51	13.605%	$83.511	$83.51	$83.50	$83.50
Purchase #5	$5.41	9.787%	$5.9395	$5.94	$5.95	$5.90
Purchase #6	$140.61	4.119%	$146.4017	$146.40	$146.40	$146.40
Purchase #7	$88.59	12.564%	$99.7204	$99.72	$99.70	$99.70
7 purchase totals =	$820.21		$869.1957	$869.19	$869.20	$869.10