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	$198.78	12.164%	$222.9596	$222.96	$222.95	$223.00
Purchase #2	$220.81	13.237%	$250.0386	$250.04	$250.05	$250.00
Purchase #3	$89.93	12.139%	$100.8466	$100.85	$100.85	$100.80
Purchase #4	$144.72	13.444%	$164.1762	$164.18	$164.20	$164.20
Purchase #5	$63.44	7.128%	$67.962	$67.96	$67.95	$68.00
Purchase #6	$246.89	7.864%	$266.3054	$266.31	$266.30	$266.30
Purchase #7	$128.52	8.387%	$139.299	$139.30	$139.30	$139.30
7 purchase totals =	$1,093.09		$1,211.5874	$1,211.60	$1,211.60	$1,211.60