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	$189.96	10.853%	$210.5764	$210.58	$210.60	$210.60
Purchase #2	$13.27	11.132%	$14.7472	$14.75	$14.75	$14.70
Purchase #3	$184.54	6.352%	$196.262	$196.26	$196.25	$196.30
Purchase #4	$184.43	4.302%	$192.3642	$192.36	$192.35	$192.40
Purchase #5	$161.60	6.781%	$172.5581	$172.56	$172.55	$172.60
Purchase #6	$133.72	4.218%	$139.3603	$139.36	$139.35	$139.40
Purchase #7	$162.57	6.107%	$172.4981	$172.50	$172.50	$172.50
7 purchase totals =	$1,030.09		$1,098.3663	$1,098.37	$1,098.35	$1,098.50