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	$76.91	5.484%	$81.1277	$81.13	$81.15	$81.10
Purchase #2	$85.84	3.737%	$89.0478	$89.05	$89.05	$89.00
Purchase #3	$132.37	6.693%	$141.2295	$141.23	$141.25	$141.20
Purchase #4	$25.63	10.316%	$28.274	$28.27	$28.25	$28.30
Purchase #5	$223.70	4.123%	$232.9232	$232.92	$232.90	$232.90
Purchase #6	$227.43	11.402%	$253.3616	$253.36	$253.35	$253.40
Purchase #7	$242.35	13.587%	$275.2781	$275.28	$275.30	$275.30
7 purchase totals =	$1,014.23		$1,101.2419	$1,101.24	$1,101.25	$1,101.20