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	$219.88	13.380%	$249.2999	$249.30	$249.30	$249.30
Purchase #2	$153.46	12.505%	$172.6502	$172.65	$172.65	$172.70
Purchase #3	$124.57	8.102%	$134.6627	$134.66	$134.65	$134.70
Purchase #4	$184.95	8.342%	$200.3785	$200.38	$200.40	$200.40
Purchase #5	$81.38	4.820%	$85.3025	$85.30	$85.30	$85.30
Purchase #6	$38.83	6.769%	$41.4584	$41.46	$41.45	$41.50
Purchase #7	$146.38	13.217%	$165.727	$165.73	$165.75	$165.70
7 purchase totals =	$949.45		$1,049.4792	$1,049.48	$1,049.50	$1,049.60