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	$186.40	13.138%	$210.8892	$210.89	$210.90	$210.90
Purchase #2	$38.31	11.377%	$42.6685	$42.67	$42.65	$42.70
Purchase #3	$87.25	7.760%	$94.0206	$94.02	$94.00	$94.00
Purchase #4	$188.85	4.766%	$197.8506	$197.85	$197.85	$197.90
Purchase #5	$13.86	7.642%	$14.9192	$14.92	$14.90	$14.90
Purchase #6	$184.78	6.396%	$196.5985	$196.60	$196.60	$196.60
Purchase #7	$176.88	13.235%	$200.2901	$200.29	$200.30	$200.30
7 purchase totals =	$876.33		$957.2367	$957.24	$957.20	$957.30