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	$163.92	6.379%	$174.3765	$174.38	$174.40	$174.40
Purchase #2	$40.96	5.218%	$43.0973	$43.10	$43.10	$43.10
Purchase #3	$24.59	4.315%	$25.6511	$25.65	$25.65	$25.70
Purchase #4	$89.59	12.158%	$100.4824	$100.48	$100.50	$100.50
Purchase #5	$221.67	13.385%	$251.3405	$251.34	$251.35	$251.30
Purchase #6	$16.42	9.111%	$17.916	$17.92	$17.90	$17.90
Purchase #7	$151.90	13.141%	$171.8612	$171.86	$171.85	$171.90
7 purchase totals =	$709.05		$784.7250	$784.73	$784.75	$784.80