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	$125.78	7.166%	$134.7934	$134.79	$134.80	$134.80
Purchase #2	$66.39	9.308%	$72.5696	$72.57	$72.55	$72.60
Purchase #3	$167.85	11.119%	$186.5132	$186.51	$186.50	$186.50
Purchase #4	$20.35	3.294%	$21.0203	$21.02	$21.00	$21.00
Purchase #5	$159.75	9.382%	$174.7377	$174.74	$174.75	$174.70
Purchase #6	$31.64	6.186%	$33.5973	$33.60	$33.60	$33.60
Purchase #7	$85.54	6.452%	$91.059	$91.06	$91.05	$91.10
7 purchase totals =	$657.30		$714.2905	$714.29	$714.25	$714.30