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	$198.39	12.618%	$223.4229	$223.42	$223.40	$223.40
Purchase #2	$219.44	12.515%	$246.9029	$246.90	$246.90	$246.90
Purchase #3	$109.47	9.296%	$119.6463	$119.65	$119.65	$119.60
Purchase #4	$82.26	10.120%	$90.5847	$90.58	$90.60	$90.60
Purchase #5	$188.45	3.787%	$195.5866	$195.59	$195.60	$195.60
Purchase #6	$189.32	13.475%	$214.8309	$214.83	$214.85	$214.80
Purchase #7	$213.27	7.836%	$229.9818	$229.98	$230.00	$230.00
7 purchase totals =	$1,200.60		$1,320.9561	$1,320.95	$1,321.00	$1,320.90