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	$59.48	7.435%	$63.9023	$63.90	$63.90	$63.90
Purchase #2	$39.48	13.109%	$44.6554	$44.66	$44.65	$44.70
Purchase #3	$135.71	5.732%	$143.4889	$143.49	$143.50	$143.50
Purchase #4	$206.27	11.402%	$229.7889	$229.79	$229.80	$229.80
Purchase #5	$168.84	10.354%	$186.3217	$186.32	$186.30	$186.30
Purchase #6	$23.71	13.432%	$26.8947	$26.89	$26.90	$26.90
Purchase #7	$101.33	4.103%	$105.4876	$105.49	$105.50	$105.50
7 purchase totals =	$734.82		$800.5395	$800.54	$800.55	$800.60