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	$193.42	13.620%	$219.7638	$219.76	$219.75	$219.80
Purchase #2	$98.43	7.634%	$105.9441	$105.94	$105.95	$105.90
Purchase #3	$228.86	5.546%	$241.5526	$241.55	$241.55	$241.60
Purchase #4	$23.29	3.710%	$24.1541	$24.15	$24.15	$24.20
Purchase #5	$145.99	11.481%	$162.7511	$162.75	$162.75	$162.80
Purchase #6	$100.97	4.873%	$105.8903	$105.89	$105.90	$105.90
Purchase #7	$89.75	6.661%	$95.7282	$95.73	$95.75	$95.70
7 purchase totals =	$880.71		$955.7842	$955.77	$955.80	$955.90