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	$147.71	13.680%	$167.9167	$167.92	$167.90	$167.90
Purchase #2	$131.49	9.124%	$143.4871	$143.49	$143.50	$143.50
Purchase #3	$231.71	5.680%	$244.8711	$244.87	$244.85	$244.90
Purchase #4	$60.58	8.783%	$65.9007	$65.90	$65.90	$65.90
Purchase #5	$90.40	10.268%	$99.6823	$99.68	$99.70	$99.70
Purchase #6	$32.72	11.278%	$36.4102	$36.41	$36.40	$36.40
Purchase #7	$240.37	4.791%	$251.8861	$251.89	$251.90	$251.90
7 purchase totals =	$934.98		$1,010.1542	$1,010.16	$1,010.15	$1,010.20