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	$126.77	11.182%	$140.9454	$140.95	$140.95	$140.90
Purchase #2	$43.68	3.431%	$45.1787	$45.18	$45.20	$45.20
Purchase #3	$6.98	7.331%	$7.4917	$7.49	$7.50	$7.50
Purchase #4	$172.71	10.760%	$191.2936	$191.29	$191.30	$191.30
Purchase #5	$25.31	4.686%	$26.496	$26.50	$26.50	$26.50
Purchase #6	$127.96	4.341%	$133.5147	$133.51	$133.50	$133.50
Purchase #7	$116.77	3.248%	$120.5627	$120.56	$120.55	$120.60
7 purchase totals =	$620.18		$665.4828	$665.48	$665.50	$665.50