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	$199.44	5.553%	$210.5149	$210.51	$210.50	$210.50
Purchase #2	$196.78	12.667%	$221.7061	$221.71	$221.70	$221.70
Purchase #3	$215.34	3.768%	$223.454	$223.45	$223.45	$223.50
Purchase #4	$106.43	10.468%	$117.5711	$117.57	$117.55	$117.60
Purchase #5	$220.35	3.271%	$227.5576	$227.56	$227.55	$227.60
Purchase #6	$29.47	10.179%	$32.4698	$32.47	$32.45	$32.50
Purchase #7	$247.36	10.515%	$273.3699	$273.37	$273.35	$273.40
7 purchase totals =	$1,215.17		$1,306.6434	$1,306.64	$1,306.55	$1,306.80