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	$78.43	7.609%	$84.3977	$84.40	$84.40	$84.40
Purchase #2	$145.49	4.430%	$151.9352	$151.94	$151.95	$151.90
Purchase #3	$178.71	10.160%	$196.8669	$196.87	$196.85	$196.90
Purchase #4	$124.51	4.334%	$129.9063	$129.91	$129.90	$129.90
Purchase #5	$195.32	9.692%	$214.2504	$214.25	$214.25	$214.30
Purchase #6	$76.74	13.191%	$86.8628	$86.86	$86.85	$86.90
Purchase #7	$140.29	12.697%	$158.1026	$158.10	$158.10	$158.10
7 purchase totals =	$939.49		$1,022.3219	$1,022.33	$1,022.30	$1,022.40