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	$109.39	4.541%	$114.3574	$114.36	$114.35	$114.40
Purchase #2	$134.74	10.493%	$148.8783	$148.88	$148.90	$148.90
Purchase #3	$187.72	8.797%	$204.2337	$204.23	$204.25	$204.20
Purchase #4	$142.29	7.821%	$153.4185	$153.42	$153.40	$153.40
Purchase #5	$147.89	13.166%	$167.3612	$167.36	$167.35	$167.40
Purchase #6	$227.69	5.579%	$240.3928	$240.39	$240.40	$240.40
Purchase #7	$194.78	9.801%	$213.8704	$213.87	$213.85	$213.90
7 purchase totals =	$1,144.50		$1,242.5123	$1,242.51	$1,242.50	$1,242.60