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	$163.54	8.180%	$176.9176	$176.92	$176.90	$176.90
Purchase #2	$156.67	9.822%	$172.0581	$172.06	$172.05	$172.10
Purchase #3	$65.46	13.503%	$74.2991	$74.30	$74.30	$74.30
Purchase #4	$213.91	9.538%	$234.3127	$234.31	$234.30	$234.30
Purchase #5	$230.30	11.672%	$257.1806	$257.18	$257.20	$257.20
Purchase #6	$156.74	10.259%	$172.82	$172.82	$172.80	$172.80
Purchase #7	$55.55	10.376%	$61.3139	$61.31	$61.30	$61.30
7 purchase totals =	$1,042.17		$1,148.9020	$1,148.90	$1,148.85	$1,148.90