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	$155.49	4.344%	$162.2445	$162.24	$162.25	$162.20
Purchase #2	$215.83	4.462%	$225.4603	$225.46	$225.45	$225.50
Purchase #3	$87.57	13.795%	$99.6503	$99.65	$99.65	$99.70
Purchase #4	$95.43	4.678%	$99.8942	$99.89	$99.90	$99.90
Purchase #5	$59.70	4.699%	$62.5053	$62.51	$62.50	$62.50
Purchase #6	$31.98	4.582%	$33.4453	$33.45	$33.45	$33.40
Purchase #7	$242.67	9.837%	$266.5414	$266.54	$266.55	$266.50
7 purchase totals =	$888.67		$949.7413	$949.74	$949.75	$949.70