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	$40.86	10.492%	$45.147	$45.15	$45.15	$45.10
Purchase #2	$109.95	9.180%	$120.0434	$120.04	$120.05	$120.00
Purchase #3	$81.79	4.874%	$85.7764	$85.78	$85.80	$85.80
Purchase #4	$15.50	10.309%	$17.0979	$17.10	$17.10	$17.10
Purchase #5	$26.60	9.221%	$29.0528	$29.05	$29.05	$29.10
Purchase #6	$68.57	5.535%	$72.3653	$72.37	$72.35	$72.40
Purchase #7	$229.59	12.424%	$258.1143	$258.11	$258.10	$258.10
7 purchase totals =	$572.86		$627.5971	$627.60	$627.60	$627.60