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	$179.59	3.358%	$185.6206	$185.62	$185.60	$185.60
Purchase #2	$250.88	9.359%	$274.3599	$274.36	$274.35	$274.40
Purchase #3	$132.73	3.828%	$137.8109	$137.81	$137.80	$137.80
Purchase #4	$204.39	5.171%	$214.959	$214.96	$214.95	$215.00
Purchase #5	$27.44	13.816%	$31.2311	$31.23	$31.25	$31.20
Purchase #6	$179.45	5.221%	$188.8191	$188.82	$188.80	$188.80
Purchase #7	$100.84	3.515%	$104.3845	$104.38	$104.40	$104.40
7 purchase totals =	$1,075.32		$1,137.1851	$1,137.18	$1,137.15	$1,137.20