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	$221.85	3.455%	$229.5149	$229.51	$229.50	$229.50
Purchase #2	$127.88	9.320%	$139.7984	$139.80	$139.80	$139.80
Purchase #3	$229.34	6.752%	$244.825	$244.83	$244.85	$244.80
Purchase #4	$203.38	9.861%	$223.4353	$223.44	$223.45	$223.40
Purchase #5	$187.45	6.102%	$198.8882	$198.89	$198.90	$198.90
Purchase #6	$234.73	12.768%	$264.7003	$264.70	$264.70	$264.70
Purchase #7	$166.98	7.380%	$179.3031	$179.30	$179.30	$179.30
7 purchase totals =	$1,371.61		$1,480.4652	$1,480.47	$1,480.50	$1,480.40