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	$69.57	12.692%	$78.3998	$78.40	$78.40	$78.40
Purchase #2	$196.90	10.468%	$217.5115	$217.51	$217.50	$217.50
Purchase #3	$89.59	12.421%	$100.718	$100.72	$100.70	$100.70
Purchase #4	$169.75	6.144%	$180.1794	$180.18	$180.20	$180.20
Purchase #5	$194.46	13.828%	$221.3499	$221.35	$221.35	$221.30
Purchase #6	$121.47	11.554%	$135.5046	$135.50	$135.50	$135.50
Purchase #7	$82.63	3.363%	$85.4088	$85.41	$85.40	$85.40
7 purchase totals =	$924.37		$1,019.0720	$1,019.07	$1,019.05	$1,019.00