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	$127.57	7.780%	$137.4949	$137.49	$137.50	$137.50
Purchase #2	$126.54	5.418%	$133.3959	$133.40	$133.40	$133.40
Purchase #3	$32.66	13.284%	$36.9986	$37.00	$37.00	$37.00
Purchase #4	$240.74	6.468%	$256.3111	$256.31	$256.30	$256.30
Purchase #5	$108.46	5.156%	$114.0522	$114.05	$114.05	$114.10
Purchase #6	$121.89	5.756%	$128.906	$128.91	$128.90	$128.90
Purchase #7	$30.81	3.494%	$31.8865	$31.89	$31.90	$31.90
7 purchase totals =	$788.67		$839.0452	$839.05	$839.05	$839.10