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	$194.67	10.754%	$215.6048	$215.60	$215.60	$215.60
Purchase #2	$198.40	11.379%	$220.9759	$220.98	$221.00	$221.00
Purchase #3	$136.38	10.342%	$150.4844	$150.48	$150.50	$150.50
Purchase #4	$186.77	12.594%	$210.2918	$210.29	$210.30	$210.30
Purchase #5	$170.66	11.305%	$189.9531	$189.95	$189.95	$190.00
Purchase #6	$175.89	9.680%	$192.9162	$192.92	$192.90	$192.90
Purchase #7	$236.67	7.848%	$255.2439	$255.24	$255.25	$255.20
7 purchase totals =	$1,299.44		$1,435.4701	$1,435.46	$1,435.50	$1,435.50