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	$195.41	9.116%	$213.2236	$213.22	$213.20	$213.20
Purchase #2	$86.75	13.687%	$98.6235	$98.62	$98.60	$98.60
Purchase #3	$195.25	11.773%	$218.2368	$218.24	$218.25	$218.20
Purchase #4	$222.61	10.426%	$245.8193	$245.82	$245.80	$245.80
Purchase #5	$198.95	10.131%	$219.1056	$219.11	$219.10	$219.10
Purchase #6	$104.67	6.528%	$111.5029	$111.50	$111.50	$111.50
Purchase #7	$139.61	11.870%	$156.1817	$156.18	$156.20	$156.20
7 purchase totals =	$1,143.25		$1,262.6934	$1,262.69	$1,262.65	$1,262.60