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	$59.35	3.483%	$61.4172	$61.42	$61.40	$61.40
Purchase #2	$187.27	13.708%	$212.941	$212.94	$212.95	$212.90
Purchase #3	$115.59	3.704%	$119.8715	$119.87	$119.85	$119.90
Purchase #4	$37.76	10.215%	$41.6172	$41.62	$41.60	$41.60
Purchase #5	$97.42	4.721%	$102.0192	$102.02	$102.00	$102.00
Purchase #6	$159.33	5.118%	$167.4845	$167.48	$167.50	$167.50
Purchase #7	$250.69	10.513%	$277.045	$277.05	$277.05	$277.00
7 purchase totals =	$907.41		$982.3956	$982.40	$982.35	$982.30