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	$237.61	7.390%	$255.1694	$255.17	$255.15	$255.20
Purchase #2	$63.69	3.404%	$65.858	$65.86	$65.85	$65.90
Purchase #3	$197.92	3.602%	$205.0491	$205.05	$205.05	$205.00
Purchase #4	$165.50	9.676%	$181.5138	$181.51	$181.50	$181.50
Purchase #5	$225.31	12.594%	$253.6855	$253.69	$253.70	$253.70
Purchase #6	$151.87	11.615%	$169.5097	$169.51	$169.50	$169.50
Purchase #7	$120.56	8.473%	$130.775	$130.78	$130.80	$130.80
7 purchase totals =	$1,162.46		$1,261.5605	$1,261.57	$1,261.55	$1,261.60