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	$196.37	10.289%	$216.5745	$216.57	$216.55	$216.60
Purchase #2	$237.70	13.806%	$270.5169	$270.52	$270.50	$270.50
Purchase #3	$39.41	10.287%	$43.4641	$43.46	$43.45	$43.50
Purchase #4	$146.25	7.486%	$157.1983	$157.20	$157.20	$157.20
Purchase #5	$30.34	4.802%	$31.7969	$31.80	$31.80	$31.80
Purchase #6	$83.62	12.549%	$94.1135	$94.11	$94.10	$94.10
Purchase #7	$52.80	12.641%	$59.4744	$59.47	$59.45	$59.50
7 purchase totals =	$786.49		$873.1386	$873.13	$873.05	$873.20