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	$145.55	5.456%	$153.4912	$153.49	$153.50	$153.50
Purchase #2	$209.65	9.680%	$229.9441	$229.94	$229.95	$229.90
Purchase #3	$64.46	11.542%	$71.9	$71.90	$71.90	$71.90
Purchase #4	$139.78	3.657%	$144.8918	$144.89	$144.90	$144.90
Purchase #5	$16.74	4.765%	$17.5377	$17.54	$17.55	$17.50
Purchase #6	$108.81	6.654%	$116.0502	$116.05	$116.05	$116.10
Purchase #7	$208.32	12.721%	$234.8204	$234.82	$234.80	$234.80
7 purchase totals =	$893.31		$968.6354	$968.63	$968.65	$968.60