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	$166.75	5.637%	$176.1497	$176.15	$176.15	$176.10
Purchase #2	$144.69	12.259%	$162.4275	$162.43	$162.45	$162.40
Purchase #3	$91.32	3.118%	$94.1674	$94.17	$94.15	$94.20
Purchase #4	$139.57	8.452%	$151.3665	$151.37	$151.35	$151.40
Purchase #5	$240.98	6.588%	$256.8558	$256.86	$256.85	$256.90
Purchase #6	$143.27	13.554%	$162.6888	$162.69	$162.70	$162.70
Purchase #7	$36.59	3.419%	$37.841	$37.84	$37.85	$37.80
7 purchase totals =	$963.17		$1,041.4967	$1,041.51	$1,041.50	$1,041.50