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	$68.69	5.533%	$72.4906	$72.49	$72.50	$72.50
Purchase #2	$220.43	6.484%	$234.7227	$234.72	$234.70	$234.70
Purchase #3	$123.78	12.645%	$139.432	$139.43	$139.45	$139.40
Purchase #4	$30.34	10.523%	$33.5327	$33.53	$33.55	$33.50
Purchase #5	$141.73	6.678%	$151.1947	$151.19	$151.20	$151.20
Purchase #6	$61.51	8.430%	$66.6953	$66.70	$66.70	$66.70
Purchase #7	$237.85	8.661%	$258.4502	$258.45	$258.45	$258.50
7 purchase totals =	$884.33		$956.5182	$956.51	$956.55	$956.50