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	$43.68	3.428%	$45.1774	$45.18	$45.20	$45.20
Purchase #2	$47.42	6.268%	$50.3923	$50.39	$50.40	$50.40
Purchase #3	$19.47	8.389%	$21.1033	$21.10	$21.10	$21.10
Purchase #4	$208.82	4.561%	$218.3443	$218.34	$218.35	$218.30
Purchase #5	$118.74	7.695%	$127.877	$127.88	$127.90	$127.90
Purchase #6	$232.87	4.600%	$243.582	$243.58	$243.60	$243.60
Purchase #7	$42.36	12.217%	$47.5351	$47.54	$47.55	$47.50
7 purchase totals =	$713.36		$754.0114	$754.01	$754.10	$754.00