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	$175.39	7.516%	$188.5723	$188.57	$188.55	$188.60
Purchase #2	$40.45	8.728%	$43.9805	$43.98	$44.00	$44.00
Purchase #3	$72.96	12.763%	$82.2719	$82.27	$82.25	$82.30
Purchase #4	$115.78	9.287%	$126.5325	$126.53	$126.55	$126.50
Purchase #5	$173.40	6.547%	$184.7525	$184.75	$184.75	$184.80
Purchase #6	$94.25	6.546%	$100.4196	$100.42	$100.40	$100.40
Purchase #7	$242.93	13.523%	$275.7814	$275.78	$275.80	$275.80
7 purchase totals =	$915.16		$1,002.3107	$1,002.30	$1,002.30	$1,002.40