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	$81.32	4.698%	$85.1404	$85.14	$85.15	$85.10
Purchase #2	$243.71	8.427%	$264.2474	$264.25	$264.25	$264.20
Purchase #3	$125.74	10.505%	$138.949	$138.95	$138.95	$138.90
Purchase #4	$211.38	13.131%	$239.1363	$239.14	$239.15	$239.10
Purchase #5	$73.62	13.188%	$83.329	$83.33	$83.35	$83.30
Purchase #6	$150.37	10.507%	$166.1694	$166.17	$166.15	$166.20
Purchase #7	$64.72	9.487%	$70.86	$70.86	$70.85	$70.90
7 purchase totals =	$950.86		$1,047.8315	$1,047.84	$1,047.85	$1,047.70