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	$182.62	8.167%	$197.5346	$197.53	$197.55	$197.50
Purchase #2	$117.69	13.608%	$133.7053	$133.71	$133.70	$133.70
Purchase #3	$52.89	8.778%	$57.5327	$57.53	$57.55	$57.50
Purchase #4	$93.88	6.373%	$99.863	$99.86	$99.85	$99.90
Purchase #5	$148.52	12.161%	$166.5815	$166.58	$166.60	$166.60
Purchase #6	$204.40	5.763%	$216.1796	$216.18	$216.20	$216.20
Purchase #7	$103.60	3.174%	$106.8883	$106.89	$106.90	$106.90
7 purchase totals =	$903.60		$978.2850	$978.28	$978.35	$978.30