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	$59.37	5.332%	$62.5356	$62.54	$62.55	$62.50
Purchase #2	$210.77	10.606%	$233.1243	$233.12	$233.10	$233.10
Purchase #3	$161.94	5.742%	$171.2386	$171.24	$171.25	$171.20
Purchase #4	$49.79	13.344%	$56.434	$56.43	$56.45	$56.40
Purchase #5	$130.92	9.431%	$143.2671	$143.27	$143.25	$143.30
Purchase #6	$154.98	7.478%	$166.5694	$166.57	$166.55	$166.60
Purchase #7	$172.57	5.591%	$182.2184	$182.22	$182.20	$182.20
7 purchase totals =	$940.34		$1,015.3874	$1,015.39	$1,015.35	$1,015.30