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	$106.76	3.331%	$110.3162	$110.32	$110.30	$110.30
Purchase #2	$79.73	11.858%	$89.1844	$89.18	$89.20	$89.20
Purchase #3	$76.95	7.724%	$82.8936	$82.89	$82.90	$82.90
Purchase #4	$116.50	12.240%	$130.7596	$130.76	$130.75	$130.80
Purchase #5	$238.66	12.171%	$267.7073	$267.71	$267.70	$267.70
Purchase #6	$91.26	8.336%	$98.8674	$98.87	$98.85	$98.90
Purchase #7	$241.96	13.523%	$274.6803	$274.68	$274.70	$274.70
7 purchase totals =	$951.82		$1,054.4088	$1,054.41	$1,054.40	$1,054.50