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	$138.71	8.583%	$150.6155	$150.62	$150.60	$150.60
Purchase #2	$103.30	3.141%	$106.5447	$106.54	$106.55	$106.50
Purchase #3	$43.60	13.748%	$49.5941	$49.59	$49.60	$49.60
Purchase #4	$81.65	9.733%	$89.597	$89.60	$89.60	$89.60
Purchase #5	$45.76	7.551%	$49.2153	$49.22	$49.20	$49.20
Purchase #6	$139.88	3.799%	$145.194	$145.19	$145.20	$145.20
Purchase #7	$100.75	9.739%	$110.562	$110.56	$110.55	$110.60
7 purchase totals =	$653.65		$701.3226	$701.32	$701.30	$701.30