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	$28.86	3.474%	$29.8626	$29.86	$29.85	$29.90
Purchase #2	$55.90	8.155%	$60.4586	$60.46	$60.45	$60.50
Purchase #3	$237.92	9.806%	$261.2504	$261.25	$261.25	$261.30
Purchase #4	$238.89	12.122%	$267.8482	$267.85	$267.85	$267.80
Purchase #5	$37.78	11.709%	$42.2037	$42.20	$42.20	$42.20
Purchase #6	$153.62	6.555%	$163.6898	$163.69	$163.70	$163.70
Purchase #7	$171.52	11.587%	$191.394	$191.39	$191.40	$191.40
7 purchase totals =	$924.49		$1,016.7073	$1,016.70	$1,016.70	$1,016.80