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	$213.80	12.772%	$241.1065	$241.11	$241.10	$241.10
Purchase #2	$120.85	6.627%	$128.8587	$128.86	$128.85	$128.90
Purchase #3	$198.52	13.686%	$225.6894	$225.69	$225.70	$225.70
Purchase #4	$49.98	13.260%	$56.6073	$56.61	$56.60	$56.60
Purchase #5	$7.31	7.342%	$7.8467	$7.85	$7.85	$7.80
Purchase #6	$139.97	3.279%	$144.5596	$144.56	$144.55	$144.60
Purchase #7	$208.50	9.772%	$228.8746	$228.87	$228.85	$228.90
7 purchase totals =	$938.93		$1,033.5428	$1,033.55	$1,033.50	$1,033.60