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	$61.63	3.736%	$63.9325	$63.93	$63.95	$63.90
Purchase #2	$179.88	3.310%	$185.834	$185.83	$185.85	$185.80
Purchase #3	$29.90	6.394%	$31.8118	$31.81	$31.80	$31.80
Purchase #4	$243.34	11.733%	$271.8911	$271.89	$271.90	$271.90
Purchase #5	$152.98	8.144%	$165.4387	$165.44	$165.45	$165.40
Purchase #6	$246.52	6.496%	$262.5339	$262.53	$262.55	$262.50
Purchase #7	$29.82	11.745%	$33.3224	$33.32	$33.30	$33.30
7 purchase totals =	$944.07		$1,014.7644	$1,014.75	$1,014.80	$1,014.60