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	$217.32	3.665%	$225.2848	$225.28	$225.30	$225.30
Purchase #2	$178.27	11.407%	$198.6053	$198.61	$198.60	$198.60
Purchase #3	$57.63	3.169%	$59.4563	$59.46	$59.45	$59.50
Purchase #4	$197.90	11.648%	$220.9514	$220.95	$220.95	$221.00
Purchase #5	$223.95	11.576%	$249.8745	$249.87	$249.85	$249.90
Purchase #6	$124.81	10.164%	$137.4957	$137.50	$137.50	$137.50
Purchase #7	$245.96	3.532%	$254.6473	$254.65	$254.65	$254.60
7 purchase totals =	$1,245.84		$1,346.3153	$1,346.32	$1,346.30	$1,346.40