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	$57.57	6.759%	$61.4612	$61.46	$61.45	$61.50
Purchase #2	$26.55	7.620%	$28.5731	$28.57	$28.55	$28.60
Purchase #3	$198.37	11.724%	$221.6269	$221.63	$221.65	$221.60
Purchase #4	$110.89	12.690%	$124.9619	$124.96	$124.95	$125.00
Purchase #5	$129.52	6.661%	$138.1473	$138.15	$138.15	$138.10
Purchase #6	$240.55	6.193%	$255.4473	$255.45	$255.45	$255.40
Purchase #7	$65.59	3.211%	$67.6961	$67.70	$67.70	$67.70
7 purchase totals =	$829.04		$897.9138	$897.92	$897.90	$897.90