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	$105.74	10.268%	$116.5974	$116.60	$116.60	$116.60
Purchase #2	$180.79	8.537%	$196.224	$196.22	$196.20	$196.20
Purchase #3	$218.61	13.529%	$248.1857	$248.19	$248.20	$248.20
Purchase #4	$26.77	12.192%	$30.0338	$30.03	$30.05	$30.00
Purchase #5	$92.51	8.758%	$100.612	$100.61	$100.60	$100.60
Purchase #6	$43.96	3.432%	$45.4687	$45.47	$45.45	$45.50
Purchase #7	$219.29	7.116%	$234.8947	$234.89	$234.90	$234.90
7 purchase totals =	$887.67		$972.0163	$972.01	$972.00	$972.00