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	$245.79	7.756%	$264.8535	$264.85	$264.85	$264.90
Purchase #2	$245.30	8.136%	$265.2576	$265.26	$265.25	$265.30
Purchase #3	$101.31	4.242%	$105.6076	$105.61	$105.60	$105.60
Purchase #4	$61.33	8.216%	$66.3689	$66.37	$66.35	$66.40
Purchase #5	$115.59	11.517%	$128.9025	$128.90	$128.90	$128.90
Purchase #6	$50.86	13.186%	$57.5664	$57.57	$57.55	$57.60
Purchase #7	$222.79	3.822%	$231.305	$231.31	$231.30	$231.30
7 purchase totals =	$1,042.97		$1,119.8615	$1,119.87	$1,119.80	$1,120.00