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	$7.32	4.790%	$7.6706	$7.67	$7.65	$7.70
Purchase #2	$77.63	6.407%	$82.6038	$82.60	$82.60	$82.60
Purchase #3	$77.90	11.115%	$86.5586	$86.56	$86.55	$86.60
Purchase #4	$64.34	10.441%	$71.0577	$71.06	$71.05	$71.10
Purchase #5	$48.97	8.836%	$53.297	$53.30	$53.30	$53.30
Purchase #6	$225.82	11.161%	$251.0238	$251.02	$251.00	$251.00
Purchase #7	$153.96	4.523%	$160.9236	$160.92	$160.90	$160.90
7 purchase totals =	$655.94		$713.1351	$713.13	$713.05	$713.20