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	$194.78	8.727%	$211.7785	$211.78	$211.80	$211.80
Purchase #2	$237.45	11.732%	$265.3076	$265.31	$265.30	$265.30
Purchase #3	$199.38	11.488%	$222.2848	$222.28	$222.30	$222.30
Purchase #4	$150.75	9.342%	$164.8331	$164.83	$164.85	$164.80
Purchase #5	$58.89	13.707%	$66.9621	$66.96	$66.95	$67.00
Purchase #6	$213.74	7.208%	$229.1464	$229.15	$229.15	$229.10
Purchase #7	$94.49	4.622%	$98.8573	$98.86	$98.85	$98.90
7 purchase totals =	$1,149.48		$1,259.1698	$1,259.17	$1,259.20	$1,259.20