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	$189.84	3.300%	$196.1047	$196.10	$196.10	$196.10
Purchase #2	$93.83	5.153%	$98.6651	$98.67	$98.65	$98.70
Purchase #3	$216.29	11.686%	$241.5656	$241.57	$241.55	$241.60
Purchase #4	$172.70	10.287%	$190.4656	$190.47	$190.45	$190.50
Purchase #5	$153.78	3.572%	$159.273	$159.27	$159.25	$159.30
Purchase #6	$75.63	5.841%	$80.0475	$80.05	$80.05	$80.00
Purchase #7	$65.75	11.846%	$73.5387	$73.54	$73.55	$73.50
7 purchase totals =	$967.82		$1,039.6602	$1,039.67	$1,039.60	$1,039.70