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	$176.39	3.448%	$182.4719	$182.47	$182.45	$182.50
Purchase #2	$95.28	4.624%	$99.6857	$99.69	$99.70	$99.70
Purchase #3	$96.46	7.828%	$104.0109	$104.01	$104.00	$104.00
Purchase #4	$141.45	7.303%	$151.7801	$151.78	$151.80	$151.80
Purchase #5	$73.77	8.302%	$79.8944	$79.89	$79.90	$79.90
Purchase #6	$117.90	13.549%	$133.8743	$133.87	$133.85	$133.90
Purchase #7	$91.36	4.153%	$95.1542	$95.15	$95.15	$95.20
7 purchase totals =	$792.61		$846.8715	$846.86	$846.85	$847.00