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	$179.47	6.346%	$190.8592	$190.86	$190.85	$190.90
Purchase #2	$28.50	4.760%	$29.8566	$29.86	$29.85	$29.90
Purchase #3	$105.55	10.231%	$116.3488	$116.35	$116.35	$116.30
Purchase #4	$218.96	13.662%	$248.8743	$248.87	$248.85	$248.90
Purchase #5	$83.85	11.212%	$93.2513	$93.25	$93.25	$93.30
Purchase #6	$196.53	12.589%	$221.2712	$221.27	$221.25	$221.30
Purchase #7	$192.72	8.425%	$208.9567	$208.96	$208.95	$209.00
7 purchase totals =	$1,005.58		$1,109.4181	$1,109.42	$1,109.35	$1,109.60