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	$149.59	13.246%	$169.4047	$169.40	$169.40	$169.40
Purchase #2	$111.66	10.571%	$123.4636	$123.46	$123.45	$123.50
Purchase #3	$140.39	7.118%	$150.383	$150.38	$150.40	$150.40
Purchase #4	$104.65	10.867%	$116.0223	$116.02	$116.00	$116.00
Purchase #5	$135.62	6.860%	$144.9235	$144.92	$144.90	$144.90
Purchase #6	$244.70	12.215%	$274.5901	$274.59	$274.60	$274.60
Purchase #7	$164.35	10.277%	$181.2402	$181.24	$181.25	$181.20
7 purchase totals =	$1,050.96		$1,160.0274	$1,160.01	$1,160.00	$1,160.00