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	$127.32	3.403%	$131.6527	$131.65	$131.65	$131.70
Purchase #2	$148.33	13.548%	$168.4257	$168.43	$168.45	$168.40
Purchase #3	$48.32	8.667%	$52.5079	$52.51	$52.50	$52.50
Purchase #4	$243.30	6.621%	$259.4089	$259.41	$259.40	$259.40
Purchase #5	$109.35	6.164%	$116.0903	$116.09	$116.10	$116.10
Purchase #6	$47.33	3.586%	$49.0273	$49.03	$49.05	$49.00
Purchase #7	$151.90	3.511%	$157.2332	$157.23	$157.25	$157.20
7 purchase totals =	$875.85		$934.3460	$934.35	$934.40	$934.30