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	$150.47	10.764%	$166.6666	$166.67	$166.65	$166.70
Purchase #2	$75.80	10.165%	$83.5051	$83.51	$83.50	$83.50
Purchase #3	$126.51	11.638%	$141.2332	$141.23	$141.25	$141.20
Purchase #4	$98.30	9.782%	$107.9157	$107.92	$107.90	$107.90
Purchase #5	$173.73	7.300%	$186.4123	$186.41	$186.40	$186.40
Purchase #6	$100.78	11.702%	$112.5733	$112.57	$112.55	$112.60
Purchase #7	$153.29	11.767%	$171.3276	$171.33	$171.35	$171.30
7 purchase totals =	$878.88		$969.6338	$969.64	$969.60	$969.60