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	$133.86	12.127%	$150.0932	$150.09	$150.10	$150.10
Purchase #2	$127.65	12.843%	$144.0441	$144.04	$144.05	$144.00
Purchase #3	$59.82	6.731%	$63.8465	$63.85	$63.85	$63.80
Purchase #4	$244.60	8.377%	$265.0901	$265.09	$265.10	$265.10
Purchase #5	$55.94	13.385%	$63.4276	$63.43	$63.45	$63.40
Purchase #6	$173.55	12.768%	$195.7089	$195.71	$195.70	$195.70
Purchase #7	$209.71	4.114%	$218.3375	$218.34	$218.35	$218.30
7 purchase totals =	$1,005.13		$1,100.5479	$1,100.55	$1,100.60	$1,100.40