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	$94.93	7.491%	$102.0412	$102.04	$102.05	$102.00
Purchase #2	$87.84	4.839%	$92.0906	$92.09	$92.10	$92.10
Purchase #3	$6.82	8.803%	$7.4204	$7.42	$7.40	$7.40
Purchase #4	$246.72	5.744%	$260.8916	$260.89	$260.90	$260.90
Purchase #5	$204.58	12.373%	$229.8927	$229.89	$229.90	$229.90
Purchase #6	$166.64	10.735%	$184.5288	$184.53	$184.55	$184.50
Purchase #7	$158.33	4.162%	$164.9197	$164.92	$164.90	$164.90
7 purchase totals =	$965.86		$1,041.7850	$1,041.78	$1,041.80	$1,041.70