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	$98.62	13.649%	$112.0806	$112.08	$112.10	$112.10
Purchase #2	$190.63	4.721%	$199.6296	$199.63	$199.65	$199.60
Purchase #3	$205.57	8.824%	$223.7095	$223.71	$223.70	$223.70
Purchase #4	$94.68	6.217%	$100.5663	$100.57	$100.55	$100.60
Purchase #5	$190.57	4.197%	$198.5682	$198.57	$198.55	$198.60
Purchase #6	$103.84	5.224%	$109.2646	$109.26	$109.25	$109.30
Purchase #7	$96.55	3.379%	$99.8124	$99.81	$99.80	$99.80
7 purchase totals =	$980.46		$1,043.6312	$1,043.63	$1,043.60	$1,043.70