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	$182.77	4.423%	$190.8539	$190.85	$190.85	$190.90
Purchase #2	$25.59	6.583%	$27.2746	$27.27	$27.25	$27.30
Purchase #3	$46.75	4.524%	$48.865	$48.87	$48.85	$48.90
Purchase #4	$209.89	5.852%	$222.1728	$222.17	$222.15	$222.20
Purchase #5	$139.87	8.204%	$151.3449	$151.34	$151.35	$151.30
Purchase #6	$149.48	13.459%	$169.5985	$169.60	$169.60	$169.60
Purchase #7	$73.72	7.655%	$79.3633	$79.36	$79.35	$79.40
7 purchase totals =	$828.07		$889.4730	$889.46	$889.40	$889.60