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	$100.34	8.529%	$108.898	$108.90	$108.90	$108.90
Purchase #2	$41.89	8.254%	$45.3476	$45.35	$45.35	$45.30
Purchase #3	$150.67	9.645%	$165.2021	$165.20	$165.20	$165.20
Purchase #4	$216.85	7.320%	$232.7234	$232.72	$232.70	$232.70
Purchase #5	$85.48	12.747%	$96.3761	$96.38	$96.40	$96.40
Purchase #6	$127.38	11.316%	$141.7943	$141.79	$141.80	$141.80
Purchase #7	$128.46	10.168%	$141.5218	$141.52	$141.50	$141.50
7 purchase totals =	$851.07		$931.8633	$931.86	$931.85	$931.80