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	$29.71	12.336%	$33.375	$33.38	$33.40	$33.40
Purchase #2	$201.39	4.265%	$209.9793	$209.98	$210.00	$210.00
Purchase #3	$227.85	9.772%	$250.1155	$250.12	$250.10	$250.10
Purchase #4	$144.59	13.811%	$164.5593	$164.56	$164.55	$164.60
Purchase #5	$192.73	6.467%	$205.1938	$205.19	$205.20	$205.20
Purchase #6	$59.50	5.708%	$62.8963	$62.90	$62.90	$62.90
Purchase #7	$102.31	8.724%	$111.2355	$111.24	$111.25	$111.20
7 purchase totals =	$958.08		$1,037.3547	$1,037.37	$1,037.40	$1,037.40