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	$181.64	8.386%	$196.8723	$196.87	$196.85	$196.90
Purchase #2	$142.64	11.755%	$159.4073	$159.41	$159.40	$159.40
Purchase #3	$192.88	11.259%	$214.5964	$214.60	$214.60	$214.60
Purchase #4	$37.65	4.710%	$39.4233	$39.42	$39.40	$39.40
Purchase #5	$229.29	6.277%	$243.6825	$243.68	$243.70	$243.70
Purchase #6	$57.51	6.143%	$61.0428	$61.04	$61.05	$61.00
Purchase #7	$135.48	11.725%	$151.365	$151.37	$151.35	$151.40
7 purchase totals =	$977.09		$1,066.3896	$1,066.39	$1,066.35	$1,066.40