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	$123.79	6.539%	$131.8846	$131.88	$131.90	$131.90
Purchase #2	$80.83	5.736%	$85.4664	$85.47	$85.45	$85.50
Purchase #3	$211.59	10.677%	$234.1815	$234.18	$234.20	$234.20
Purchase #4	$105.68	13.189%	$119.6181	$119.62	$119.60	$119.60
Purchase #5	$29.69	3.816%	$30.823	$30.82	$30.80	$30.80
Purchase #6	$217.87	8.456%	$236.2931	$236.29	$236.30	$236.30
Purchase #7	$201.96	10.279%	$222.7195	$222.72	$222.70	$222.70
7 purchase totals =	$971.41		$1,060.9862	$1,060.98	$1,060.95	$1,061.00