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	$29.84	13.393%	$33.8365	$33.84	$33.85	$33.80
Purchase #2	$168.92	10.382%	$186.4573	$186.46	$186.45	$186.50
Purchase #3	$137.48	11.438%	$153.205	$153.21	$153.20	$153.20
Purchase #4	$83.34	4.240%	$86.8736	$86.87	$86.85	$86.90
Purchase #5	$197.27	12.779%	$222.4791	$222.48	$222.50	$222.50
Purchase #6	$241.62	9.603%	$264.8228	$264.82	$264.80	$264.80
Purchase #7	$229.76	3.301%	$237.3444	$237.34	$237.35	$237.30
7 purchase totals =	$1,088.23		$1,185.0187	$1,185.02	$1,185.00	$1,185.00