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	$41.26	5.319%	$43.4546	$43.45	$43.45	$43.50
Purchase #2	$120.75	5.429%	$127.3055	$127.31	$127.30	$127.30
Purchase #3	$21.79	3.321%	$22.5136	$22.51	$22.50	$22.50
Purchase #4	$157.53	13.849%	$179.3463	$179.35	$179.35	$179.30
Purchase #5	$6.59	11.864%	$7.3718	$7.37	$7.35	$7.40
Purchase #6	$88.43	4.489%	$92.3996	$92.40	$92.40	$92.40
Purchase #7	$169.65	11.234%	$188.7085	$188.71	$188.70	$188.70
7 purchase totals =	$606.00		$661.0999	$661.10	$661.05	$661.10