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	$242.69	4.151%	$252.7641	$252.76	$252.75	$252.80
Purchase #2	$123.56	10.274%	$136.2546	$136.25	$136.25	$136.30
Purchase #3	$76.33	8.322%	$82.6822	$82.68	$82.70	$82.70
Purchase #4	$212.52	5.709%	$224.6528	$224.65	$224.65	$224.70
Purchase #5	$146.81	5.502%	$154.8875	$154.89	$154.90	$154.90
Purchase #6	$179.48	5.736%	$189.775	$189.78	$189.80	$189.80
Purchase #7	$35.48	5.766%	$37.5258	$37.53	$37.55	$37.50
7 purchase totals =	$1,016.87		$1,078.5420	$1,078.54	$1,078.60	$1,078.70