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	$200.90	9.124%	$219.2301	$219.23	$219.25	$219.20
Purchase #2	$92.91	11.211%	$103.3261	$103.33	$103.35	$103.30
Purchase #3	$159.55	7.690%	$171.8194	$171.82	$171.80	$171.80
Purchase #4	$141.72	3.425%	$146.5739	$146.57	$146.55	$146.60
Purchase #5	$124.34	11.378%	$138.4874	$138.49	$138.50	$138.50
Purchase #6	$74.27	7.769%	$80.04	$80.04	$80.05	$80.00
Purchase #7	$78.66	8.480%	$85.3304	$85.33	$85.35	$85.30
7 purchase totals =	$872.35		$944.8073	$944.81	$944.85	$944.70