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	$191.87	10.387%	$211.7995	$211.80	$211.80	$211.80
Purchase #2	$80.94	6.733%	$86.3897	$86.39	$86.40	$86.40
Purchase #3	$200.32	12.448%	$225.2558	$225.26	$225.25	$225.30
Purchase #4	$69.92	12.457%	$78.6299	$78.63	$78.65	$78.60
Purchase #5	$151.48	8.340%	$164.1134	$164.11	$164.10	$164.10
Purchase #6	$145.35	4.118%	$151.3355	$151.34	$151.35	$151.30
Purchase #7	$125.46	10.872%	$139.1	$139.10	$139.10	$139.10
7 purchase totals =	$965.34		$1,056.6238	$1,056.63	$1,056.65	$1,056.60