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	$95.52	8.246%	$103.3966	$103.40	$103.40	$103.40
Purchase #2	$106.75	11.570%	$119.101	$119.10	$119.10	$119.10
Purchase #3	$115.56	9.614%	$126.6699	$126.67	$126.65	$126.70
Purchase #4	$227.35	10.134%	$250.3896	$250.39	$250.40	$250.40
Purchase #5	$213.55	7.284%	$229.105	$229.11	$229.10	$229.10
Purchase #6	$92.30	6.277%	$98.0937	$98.09	$98.10	$98.10
Purchase #7	$164.60	4.363%	$171.7815	$171.78	$171.80	$171.80
7 purchase totals =	$1,015.63		$1,098.5373	$1,098.54	$1,098.55	$1,098.60