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	$193.54	3.763%	$200.8229	$200.82	$200.80	$200.80
Purchase #2	$39.43	7.559%	$42.4105	$42.41	$42.40	$42.40
Purchase #3	$183.36	9.224%	$200.2731	$200.27	$200.25	$200.30
Purchase #4	$167.70	10.576%	$185.436	$185.44	$185.45	$185.40
Purchase #5	$40.82	6.765%	$43.5815	$43.58	$43.60	$43.60
Purchase #6	$93.39	10.407%	$103.1091	$103.11	$103.10	$103.10
Purchase #7	$113.90	11.306%	$126.7775	$126.78	$126.80	$126.80
7 purchase totals =	$832.14		$902.4106	$902.41	$902.40	$902.40