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	$156.83	6.783%	$167.4678	$167.47	$167.45	$167.50
Purchase #2	$174.43	5.792%	$184.533	$184.53	$184.55	$184.50
Purchase #3	$42.96	11.856%	$48.0533	$48.05	$48.05	$48.10
Purchase #4	$239.47	12.529%	$269.4732	$269.47	$269.45	$269.50
Purchase #5	$244.25	13.385%	$276.9429	$276.94	$276.95	$276.90
Purchase #6	$208.70	6.853%	$223.0022	$223.00	$223.00	$223.00
Purchase #7	$75.46	13.332%	$85.5203	$85.52	$85.50	$85.50
7 purchase totals =	$1,142.10		$1,254.9927	$1,254.98	$1,254.95	$1,255.00