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	$82.78	11.477%	$92.2807	$92.28	$92.30	$92.30
Purchase #2	$240.61	8.843%	$261.8871	$261.89	$261.90	$261.90
Purchase #3	$206.51	5.573%	$218.0188	$218.02	$218.00	$218.00
Purchase #4	$52.52	13.489%	$59.6044	$59.60	$59.60	$59.60
Purchase #5	$135.37	11.523%	$150.9687	$150.97	$150.95	$151.00
Purchase #6	$170.29	10.587%	$188.3186	$188.32	$188.30	$188.30
Purchase #7	$219.45	3.806%	$227.8023	$227.80	$227.80	$227.80
7 purchase totals =	$1,107.53		$1,198.8806	$1,198.88	$1,198.85	$1,198.90