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	$195.34	11.773%	$218.3374	$218.34	$218.35	$218.30
Purchase #2	$115.56	10.232%	$127.3841	$127.38	$127.40	$127.40
Purchase #3	$29.52	9.530%	$32.3333	$32.33	$32.35	$32.30
Purchase #4	$139.28	8.371%	$150.9391	$150.94	$150.95	$150.90
Purchase #5	$236.29	3.457%	$244.4585	$244.46	$244.45	$244.50
Purchase #6	$99.74	12.827%	$112.5336	$112.53	$112.55	$112.50
Purchase #7	$227.84	13.260%	$258.0516	$258.05	$258.05	$258.10
7 purchase totals =	$1,043.57		$1,144.0376	$1,144.03	$1,144.10	$1,144.00