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	$155.43	11.789%	$173.7536	$173.75	$173.75	$173.80
Purchase #2	$78.29	9.552%	$85.7683	$85.77	$85.75	$85.80
Purchase #3	$239.90	4.656%	$251.0697	$251.07	$251.05	$251.10
Purchase #4	$209.31	6.687%	$223.3066	$223.31	$223.30	$223.30
Purchase #5	$115.37	6.635%	$123.0248	$123.02	$123.00	$123.00
Purchase #6	$37.98	5.317%	$39.9994	$40.00	$40.00	$40.00
Purchase #7	$148.65	6.847%	$158.8281	$158.83	$158.85	$158.80
7 purchase totals =	$984.93		$1,055.7505	$1,055.75	$1,055.70	$1,055.80