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	$94.42	4.298%	$98.4782	$98.48	$98.50	$98.50
Purchase #2	$160.82	13.479%	$182.4969	$182.50	$182.50	$182.50
Purchase #3	$105.57	13.544%	$119.8684	$119.87	$119.85	$119.90
Purchase #4	$109.28	8.169%	$118.2071	$118.21	$118.20	$118.20
Purchase #5	$89.95	9.468%	$98.4665	$98.47	$98.45	$98.50
Purchase #6	$213.73	7.426%	$229.6016	$229.60	$229.60	$229.60
Purchase #7	$135.68	12.603%	$152.7798	$152.78	$152.80	$152.80
7 purchase totals =	$909.45		$999.8985	$999.91	$999.90	$1,000.00