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	$85.34	11.841%	$95.4451	$95.45	$95.45	$95.40
Purchase #2	$95.71	10.134%	$105.4093	$105.41	$105.40	$105.40
Purchase #3	$139.79	8.312%	$151.4093	$151.41	$151.40	$151.40
Purchase #4	$37.96	11.691%	$42.3979	$42.40	$42.40	$42.40
Purchase #5	$46.55	9.864%	$51.1417	$51.14	$51.15	$51.10
Purchase #6	$188.93	9.242%	$206.3909	$206.39	$206.40	$206.40
Purchase #7	$194.99	12.841%	$220.0287	$220.03	$220.05	$220.00
7 purchase totals =	$789.27		$872.2229	$872.23	$872.25	$872.10