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	$201.96	12.580%	$227.3666	$227.37	$227.35	$227.40
Purchase #2	$134.59	3.642%	$139.4918	$139.49	$139.50	$139.50
Purchase #3	$52.58	5.743%	$55.5997	$55.60	$55.60	$55.60
Purchase #4	$237.34	4.686%	$248.4618	$248.46	$248.45	$248.50
Purchase #5	$222.93	4.260%	$232.4268	$232.43	$232.45	$232.40
Purchase #6	$27.89	8.455%	$30.2481	$30.25	$30.25	$30.20
Purchase #7	$80.77	5.869%	$85.5104	$85.51	$85.50	$85.50
7 purchase totals =	$958.06		$1,019.1052	$1,019.11	$1,019.10	$1,019.10