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	$80.70	10.555%	$89.2179	$89.22	$89.20	$89.20
Purchase #2	$27.72	4.254%	$28.8992	$28.90	$28.90	$28.90
Purchase #3	$155.95	5.421%	$164.404	$164.40	$164.40	$164.40
Purchase #4	$233.78	4.316%	$243.8699	$243.87	$243.85	$243.90
Purchase #5	$65.81	13.776%	$74.876	$74.88	$74.90	$74.90
Purchase #6	$132.86	11.136%	$147.6553	$147.66	$147.65	$147.70
Purchase #7	$34.32	9.757%	$37.6686	$37.67	$37.65	$37.70
7 purchase totals =	$731.14		$786.5909	$786.60	$786.55	$786.70