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	$45.87	3.714%	$47.5736	$47.57	$47.55	$47.60
Purchase #2	$97.41	3.596%	$100.9129	$100.91	$100.90	$100.90
Purchase #3	$243.67	8.705%	$264.8815	$264.88	$264.90	$264.90
Purchase #4	$77.33	13.848%	$88.0387	$88.04	$88.05	$88.00
Purchase #5	$112.63	10.509%	$124.4663	$124.47	$124.45	$124.50
Purchase #6	$110.87	11.644%	$123.7797	$123.78	$123.80	$123.80
Purchase #7	$157.59	7.642%	$169.633	$169.63	$169.65	$169.60
7 purchase totals =	$845.37		$919.2857	$919.28	$919.30	$919.30