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	$213.38	5.849%	$225.8606	$225.86	$225.85	$225.90
Purchase #2	$146.79	10.233%	$161.811	$161.81	$161.80	$161.80
Purchase #3	$52.72	10.787%	$58.4069	$58.41	$58.40	$58.40
Purchase #4	$189.79	12.178%	$212.9026	$212.90	$212.90	$212.90
Purchase #5	$160.65	13.611%	$182.5161	$182.52	$182.50	$182.50
Purchase #6	$45.83	5.322%	$48.2691	$48.27	$48.25	$48.30
Purchase #7	$85.26	4.656%	$89.2297	$89.23	$89.25	$89.20
7 purchase totals =	$894.42		$978.9960	$979.00	$978.95	$979.00