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	$81.97	13.131%	$92.7335	$92.73	$92.75	$92.70
Purchase #2	$62.91	6.512%	$67.0067	$67.01	$67.00	$67.00
Purchase #3	$184.77	8.126%	$199.7844	$199.78	$199.80	$199.80
Purchase #4	$77.66	11.480%	$86.5754	$86.58	$86.60	$86.60
Purchase #5	$7.68	3.310%	$7.9342	$7.93	$7.95	$7.90
Purchase #6	$145.34	3.585%	$150.5504	$150.55	$150.55	$150.60
Purchase #7	$54.89	5.338%	$57.82	$57.82	$57.80	$57.80
7 purchase totals =	$615.22		$662.4046	$662.40	$662.45	$662.40