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	$171.28	7.236%	$183.6738	$183.67	$183.65	$183.70
Purchase #2	$198.95	4.800%	$208.4996	$208.50	$208.50	$208.50
Purchase #3	$53.29	11.631%	$59.4882	$59.49	$59.50	$59.50
Purchase #4	$204.93	6.346%	$217.9349	$217.93	$217.95	$217.90
Purchase #5	$134.86	5.230%	$141.9132	$141.91	$141.90	$141.90
Purchase #6	$226.64	10.369%	$250.1403	$250.14	$250.15	$250.10
Purchase #7	$53.54	7.182%	$57.3852	$57.39	$57.40	$57.40
7 purchase totals =	$1,043.49		$1,119.0352	$1,119.03	$1,119.05	$1,119.00