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	$54.62	8.170%	$59.0825	$59.08	$59.10	$59.10
Purchase #2	$63.95	4.700%	$66.9557	$66.96	$66.95	$67.00
Purchase #3	$85.52	11.673%	$95.5027	$95.50	$95.50	$95.50
Purchase #4	$42.99	12.780%	$48.4841	$48.48	$48.50	$48.50
Purchase #5	$152.80	11.158%	$169.8494	$169.85	$169.85	$169.80
Purchase #6	$26.97	5.495%	$28.452	$28.45	$28.45	$28.50
Purchase #7	$238.48	12.424%	$268.1088	$268.11	$268.10	$268.10
7 purchase totals =	$665.33		$736.4352	$736.43	$736.45	$736.50