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	$163.86	4.749%	$171.6417	$171.64	$171.65	$171.60
Purchase #2	$136.75	12.504%	$153.8492	$153.85	$153.85	$153.80
Purchase #3	$177.50	4.356%	$185.2319	$185.23	$185.25	$185.20
Purchase #4	$73.78	11.188%	$82.0345	$82.03	$82.05	$82.00
Purchase #5	$212.87	8.250%	$230.4318	$230.43	$230.45	$230.40
Purchase #6	$112.78	3.154%	$116.3371	$116.34	$116.35	$116.30
Purchase #7	$216.46	8.218%	$234.2487	$234.25	$234.25	$234.20
7 purchase totals =	$1,094.00		$1,173.7749	$1,173.77	$1,173.85	$1,173.50