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	$59.62	9.468%	$65.2648	$65.26	$65.25	$65.30
Purchase #2	$196.64	13.296%	$222.7853	$222.79	$222.80	$222.80
Purchase #3	$188.33	8.735%	$204.7806	$204.78	$204.80	$204.80
Purchase #4	$198.89	11.820%	$222.3988	$222.40	$222.40	$222.40
Purchase #5	$250.79	6.261%	$266.492	$266.49	$266.50	$266.50
Purchase #6	$67.47	6.777%	$72.0424	$72.04	$72.05	$72.00
Purchase #7	$102.49	12.719%	$115.5257	$115.53	$115.55	$115.50
7 purchase totals =	$1,064.23		$1,169.2896	$1,169.29	$1,169.35	$1,169.30