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	$196.44	12.751%	$221.4881	$221.49	$221.50	$221.50
Purchase #2	$200.70	7.394%	$215.5398	$215.54	$215.55	$215.50
Purchase #3	$37.81	3.545%	$39.1504	$39.15	$39.15	$39.20
Purchase #4	$117.41	5.557%	$123.9345	$123.93	$123.95	$123.90
Purchase #5	$94.63	7.272%	$101.5115	$101.51	$101.50	$101.50
Purchase #6	$152.87	9.193%	$166.9233	$166.92	$166.90	$166.90
Purchase #7	$106.74	6.346%	$113.5137	$113.51	$113.50	$113.50
7 purchase totals =	$906.60		$982.0613	$982.05	$982.05	$982.00