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	$184.46	6.713%	$196.8428	$196.84	$196.85	$196.80
Purchase #2	$220.89	5.710%	$233.5028	$233.50	$233.50	$233.50
Purchase #3	$84.68	6.733%	$90.3815	$90.38	$90.40	$90.40
Purchase #4	$96.93	7.655%	$104.35	$104.35	$104.35	$104.40
Purchase #5	$204.42	4.216%	$213.0383	$213.04	$213.05	$213.00
Purchase #6	$131.39	4.754%	$137.6363	$137.64	$137.65	$137.60
Purchase #7	$235.34	4.439%	$245.7867	$245.79	$245.80	$245.80
7 purchase totals =	$1,158.11		$1,221.5384	$1,221.54	$1,221.60	$1,221.50