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	$99.63	11.570%	$111.1572	$111.16	$111.15	$111.20
Purchase #2	$131.50	11.621%	$146.7816	$146.78	$146.80	$146.80
Purchase #3	$199.54	3.188%	$205.9013	$205.90	$205.90	$205.90
Purchase #4	$138.33	4.793%	$144.9602	$144.96	$144.95	$145.00
Purchase #5	$225.57	8.364%	$244.4367	$244.44	$244.45	$244.40
Purchase #6	$48.36	6.871%	$51.6828	$51.68	$51.70	$51.70
Purchase #7	$29.53	9.660%	$32.3826	$32.38	$32.40	$32.40
7 purchase totals =	$872.46		$937.3024	$937.30	$937.35	$937.40