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	$172.26	7.310%	$184.8522	$184.85	$184.85	$184.90
Purchase #2	$179.52	9.462%	$196.5062	$196.51	$196.50	$196.50
Purchase #3	$7.36	3.362%	$7.6074	$7.61	$7.60	$7.60
Purchase #4	$156.73	13.215%	$177.4419	$177.44	$177.45	$177.40
Purchase #5	$68.55	13.465%	$77.7803	$77.78	$77.80	$77.80
Purchase #6	$121.83	8.443%	$132.1161	$132.12	$132.10	$132.10
Purchase #7	$44.93	3.398%	$46.4567	$46.46	$46.45	$46.50
7 purchase totals =	$751.18		$822.7608	$822.77	$822.75	$822.80