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	$191.43	12.145%	$214.6792	$214.68	$214.70	$214.70
Purchase #2	$31.67	13.143%	$35.8324	$35.83	$35.85	$35.80
Purchase #3	$31.44	5.412%	$33.1415	$33.14	$33.15	$33.10
Purchase #4	$155.67	5.505%	$164.2396	$164.24	$164.25	$164.20
Purchase #5	$67.45	7.731%	$72.6646	$72.66	$72.65	$72.70
Purchase #6	$248.50	10.177%	$273.7898	$273.79	$273.80	$273.80
Purchase #7	$52.52	3.412%	$54.312	$54.31	$54.30	$54.30
7 purchase totals =	$778.68		$848.6591	$848.65	$848.70	$848.60