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	$190.50	9.687%	$208.9537	$208.95	$208.95	$209.00
Purchase #2	$100.66	10.617%	$111.3471	$111.35	$111.35	$111.30
Purchase #3	$221.78	13.139%	$250.9197	$250.92	$250.90	$250.90
Purchase #4	$153.90	3.526%	$159.3265	$159.33	$159.35	$159.30
Purchase #5	$209.89	3.749%	$217.7588	$217.76	$217.75	$217.80
Purchase #6	$109.46	3.768%	$113.5845	$113.58	$113.60	$113.60
Purchase #7	$183.44	4.544%	$191.7755	$191.78	$191.80	$191.80
7 purchase totals =	$1,169.63		$1,253.6658	$1,253.67	$1,253.70	$1,253.70