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	$131.47	12.238%	$147.5593	$147.56	$147.55	$147.60
Purchase #2	$57.95	9.616%	$63.5225	$63.52	$63.50	$63.50
Purchase #3	$16.53	6.786%	$17.6517	$17.65	$17.65	$17.70
Purchase #4	$178.34	10.253%	$196.6252	$196.63	$196.65	$196.60
Purchase #5	$32.25	4.395%	$33.6674	$33.67	$33.65	$33.70
Purchase #6	$208.58	5.695%	$220.4586	$220.46	$220.45	$220.50
Purchase #7	$64.47	3.663%	$66.8315	$66.83	$66.85	$66.80
7 purchase totals =	$689.59		$746.3162	$746.32	$746.30	$746.40