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	$227.46	8.614%	$247.0534	$247.05	$247.05	$247.10
Purchase #2	$150.70	10.189%	$166.0548	$166.05	$166.05	$166.10
Purchase #3	$100.63	3.363%	$104.0142	$104.01	$104.00	$104.00
Purchase #4	$42.29	9.485%	$46.3012	$46.30	$46.30	$46.30
Purchase #5	$134.90	10.824%	$149.5016	$149.50	$149.50	$149.50
Purchase #6	$182.75	7.530%	$196.5111	$196.51	$196.50	$196.50
Purchase #7	$124.48	13.174%	$140.879	$140.88	$140.90	$140.90
7 purchase totals =	$963.21		$1,050.3153	$1,050.30	$1,050.30	$1,050.40