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	$119.41	3.310%	$123.3625	$123.36	$123.35	$123.40
Purchase #2	$250.51	5.853%	$265.1724	$265.17	$265.15	$265.20
Purchase #3	$133.81	12.649%	$150.7356	$150.74	$150.75	$150.70
Purchase #4	$241.75	13.635%	$274.7126	$274.71	$274.70	$274.70
Purchase #5	$139.39	13.792%	$158.6147	$158.61	$158.60	$158.60
Purchase #6	$224.98	7.610%	$242.101	$242.10	$242.10	$242.10
Purchase #7	$80.68	6.124%	$85.6208	$85.62	$85.60	$85.60
7 purchase totals =	$1,190.53		$1,300.3196	$1,300.31	$1,300.25	$1,300.30