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	$74.66	5.743%	$78.9477	$78.95	$78.95	$78.90
Purchase #2	$223.37	11.706%	$249.5177	$249.52	$249.50	$249.50
Purchase #3	$140.31	11.422%	$156.3362	$156.34	$156.35	$156.30
Purchase #4	$58.60	4.210%	$61.0671	$61.07	$61.05	$61.10
Purchase #5	$169.55	11.801%	$189.5586	$189.56	$189.55	$189.60
Purchase #6	$74.37	11.363%	$82.8207	$82.82	$82.80	$82.80
Purchase #7	$235.62	12.833%	$265.8571	$265.86	$265.85	$265.90
7 purchase totals =	$976.48		$1,084.1051	$1,084.12	$1,084.05	$1,084.10