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	$162.83	11.515%	$181.5799	$181.58	$181.60	$181.60
Purchase #2	$239.37	10.431%	$264.3387	$264.34	$264.35	$264.30
Purchase #3	$82.93	3.245%	$85.6211	$85.62	$85.60	$85.60
Purchase #4	$88.48	10.731%	$97.9748	$97.97	$97.95	$98.00
Purchase #5	$105.47	10.468%	$116.5106	$116.51	$116.50	$116.50
Purchase #6	$143.40	3.601%	$148.5638	$148.56	$148.55	$148.60
Purchase #7	$118.48	8.496%	$128.5461	$128.55	$128.55	$128.50
7 purchase totals =	$940.96		$1,023.1350	$1,023.13	$1,023.10	$1,023.10