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	$189.45	3.621%	$196.31	$196.31	$196.30	$196.30
Purchase #2	$228.67	11.465%	$254.887	$254.89	$254.90	$254.90
Purchase #3	$130.89	3.468%	$135.4293	$135.43	$135.45	$135.40
Purchase #4	$82.47	8.484%	$89.4668	$89.47	$89.45	$89.50
Purchase #5	$48.87	5.569%	$51.5916	$51.59	$51.60	$51.60
Purchase #6	$16.94	8.788%	$18.4287	$18.43	$18.45	$18.40
Purchase #7	$58.45	9.654%	$64.0928	$64.09	$64.10	$64.10
7 purchase totals =	$755.74		$810.2062	$810.21	$810.25	$810.20