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	$59.38	13.704%	$67.5174	$67.52	$67.50	$67.50
Purchase #2	$205.96	4.500%	$215.2282	$215.23	$215.25	$215.20
Purchase #3	$222.52	4.598%	$232.7515	$232.75	$232.75	$232.80
Purchase #4	$160.95	6.423%	$171.2878	$171.29	$171.30	$171.30
Purchase #5	$122.75	11.203%	$136.5017	$136.50	$136.50	$136.50
Purchase #6	$58.38	13.653%	$66.3506	$66.35	$66.35	$66.40
Purchase #7	$125.94	4.695%	$131.8529	$131.85	$131.85	$131.90
7 purchase totals =	$955.88		$1,021.4901	$1,021.49	$1,021.50	$1,021.60