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	$242.94	3.289%	$250.9303	$250.93	$250.95	$250.90
Purchase #2	$34.94	4.716%	$36.5878	$36.59	$36.60	$36.60
Purchase #3	$100.30	5.562%	$105.8787	$105.88	$105.90	$105.90
Purchase #4	$108.31	11.329%	$120.5804	$120.58	$120.60	$120.60
Purchase #5	$239.52	9.674%	$262.6912	$262.69	$262.70	$262.70
Purchase #6	$116.56	3.187%	$120.2748	$120.27	$120.25	$120.30
Purchase #7	$42.60	7.477%	$45.7852	$45.79	$45.80	$45.80
7 purchase totals =	$885.17		$942.7284	$942.73	$942.80	$942.80