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	$41.81	11.319%	$46.5425	$46.54	$46.55	$46.50
Purchase #2	$102.40	8.505%	$111.1091	$111.11	$111.10	$111.10
Purchase #3	$60.48	10.225%	$66.6641	$66.66	$66.65	$66.70
Purchase #4	$245.62	13.838%	$279.6089	$279.61	$279.60	$279.60
Purchase #5	$92.42	6.683%	$98.5964	$98.60	$98.60	$98.60
Purchase #6	$228.66	3.268%	$236.1326	$236.13	$236.15	$236.10
Purchase #7	$13.38	3.589%	$13.8602	$13.86	$13.85	$13.90
7 purchase totals =	$784.77		$852.5138	$852.51	$852.50	$852.50