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	$42.77	11.553%	$47.7112	$47.71	$47.70	$47.70
Purchase #2	$89.98	11.857%	$100.6489	$100.65	$100.65	$100.60
Purchase #3	$113.56	11.185%	$126.2617	$126.26	$126.25	$126.30
Purchase #4	$80.95	3.853%	$84.069	$84.07	$84.05	$84.10
Purchase #5	$169.79	9.406%	$185.7604	$185.76	$185.75	$185.80
Purchase #6	$198.59	13.363%	$225.1276	$225.13	$225.15	$225.10
Purchase #7	$140.53	12.839%	$158.5726	$158.57	$158.55	$158.60
7 purchase totals =	$836.17		$928.1514	$928.15	$928.10	$928.20