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	$232.87	10.162%	$256.5342	$256.53	$256.55	$256.50
Purchase #2	$158.63	13.132%	$179.4613	$179.46	$179.45	$179.50
Purchase #3	$26.95	9.279%	$29.4507	$29.45	$29.45	$29.50
Purchase #4	$127.74	7.480%	$137.295	$137.30	$137.30	$137.30
Purchase #5	$16.73	8.145%	$18.0927	$18.09	$18.10	$18.10
Purchase #6	$236.48	11.792%	$264.3657	$264.37	$264.35	$264.40
Purchase #7	$249.36	5.227%	$262.394	$262.39	$262.40	$262.40
7 purchase totals =	$1,048.76		$1,147.5936	$1,147.59	$1,147.60	$1,147.70