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	$211.79	3.270%	$218.7155	$218.72	$218.70	$218.70
Purchase #2	$146.66	12.171%	$164.51	$164.51	$164.50	$164.50
Purchase #3	$209.69	3.675%	$217.3961	$217.40	$217.40	$217.40
Purchase #4	$66.47	10.423%	$73.3982	$73.40	$73.40	$73.40
Purchase #5	$184.42	6.592%	$196.577	$196.58	$196.60	$196.60
Purchase #6	$83.41	12.314%	$93.6811	$93.68	$93.70	$93.70
Purchase #7	$212.55	4.239%	$221.56	$221.56	$221.55	$221.60
7 purchase totals =	$1,114.99		$1,185.8379	$1,185.85	$1,185.85	$1,185.90