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	$144.76	7.165%	$155.1321	$155.13	$155.15	$155.10
Purchase #2	$246.69	6.799%	$263.4625	$263.46	$263.45	$263.50
Purchase #3	$38.65	10.526%	$42.7183	$42.72	$42.70	$42.70
Purchase #4	$59.75	5.637%	$63.1181	$63.12	$63.10	$63.10
Purchase #5	$108.31	4.220%	$112.8807	$112.88	$112.90	$112.90
Purchase #6	$70.79	10.163%	$77.9844	$77.98	$78.00	$78.00
Purchase #7	$169.88	12.462%	$191.0504	$191.05	$191.05	$191.10
7 purchase totals =	$838.83		$906.3465	$906.34	$906.35	$906.40