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	$123.55	5.312%	$130.113	$130.11	$130.10	$130.10
Purchase #2	$128.41	8.383%	$139.1746	$139.17	$139.15	$139.20
Purchase #3	$120.71	13.631%	$137.164	$137.16	$137.15	$137.20
Purchase #4	$60.81	10.524%	$67.2096	$67.21	$67.20	$67.20
Purchase #5	$81.86	12.590%	$92.1662	$92.17	$92.15	$92.20
Purchase #6	$49.61	11.574%	$55.3519	$55.35	$55.35	$55.40
Purchase #7	$82.77	4.153%	$86.2074	$86.21	$86.20	$86.20
7 purchase totals =	$647.72		$707.3867	$707.38	$707.30	$707.50