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	$195.48	8.799%	$212.6803	$212.68	$212.70	$212.70
Purchase #2	$178.25	12.310%	$200.1926	$200.19	$200.20	$200.20
Purchase #3	$143.71	5.387%	$151.4517	$151.45	$151.45	$151.50
Purchase #4	$209.53	11.527%	$233.6825	$233.68	$233.70	$233.70
Purchase #5	$56.59	5.136%	$59.4965	$59.50	$59.50	$59.50
Purchase #6	$249.49	13.824%	$283.9795	$283.98	$284.00	$284.00
Purchase #7	$145.61	7.465%	$156.4798	$156.48	$156.50	$156.50
7 purchase totals =	$1,178.66		$1,297.9629	$1,297.96	$1,298.05	$1,298.10