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	$55.48	6.847%	$59.2787	$59.28	$59.30	$59.30
Purchase #2	$134.78	12.547%	$151.6908	$151.69	$151.70	$151.70
Purchase #3	$78.71	10.566%	$87.0265	$87.03	$87.05	$87.00
Purchase #4	$224.27	6.476%	$238.7937	$238.79	$238.80	$238.80
Purchase #5	$31.58	8.567%	$34.2855	$34.29	$34.30	$34.30
Purchase #6	$212.41	3.645%	$220.1523	$220.15	$220.15	$220.20
Purchase #7	$198.29	13.504%	$225.0671	$225.07	$225.05	$225.10
7 purchase totals =	$935.52		$1,016.2946	$1,016.30	$1,016.35	$1,016.40