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	$136.80	3.122%	$141.0709	$141.07	$141.05	$141.10
Purchase #2	$46.32	10.279%	$51.0812	$51.08	$51.10	$51.10
Purchase #3	$21.77	11.706%	$24.3184	$24.32	$24.30	$24.30
Purchase #4	$206.28	6.583%	$219.8594	$219.86	$219.85	$219.90
Purchase #5	$36.49	7.797%	$39.3351	$39.34	$39.35	$39.30
Purchase #6	$53.59	10.477%	$59.2046	$59.20	$59.20	$59.20
Purchase #7	$136.42	10.347%	$150.5354	$150.54	$150.55	$150.50
7 purchase totals =	$637.67		$685.4050	$685.41	$685.40	$685.40