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	$198.78	12.583%	$223.7925	$223.79	$223.80	$223.80
Purchase #2	$48.79	9.245%	$53.3006	$53.30	$53.30	$53.30
Purchase #3	$37.48	13.385%	$42.4967	$42.50	$42.50	$42.50
Purchase #4	$198.57	9.482%	$217.3984	$217.40	$217.40	$217.40
Purchase #5	$168.61	4.285%	$175.8349	$175.83	$175.85	$175.80
Purchase #6	$238.78	7.723%	$257.221	$257.22	$257.20	$257.20
Purchase #7	$244.63	13.585%	$277.863	$277.86	$277.85	$277.90
7 purchase totals =	$1,135.64		$1,247.9071	$1,247.90	$1,247.90	$1,247.90