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	$61.87	12.662%	$69.704	$69.70	$69.70	$69.70
Purchase #2	$72.91	12.604%	$82.0996	$82.10	$82.10	$82.10
Purchase #3	$96.27	9.492%	$105.4079	$105.41	$105.40	$105.40
Purchase #4	$33.79	4.131%	$35.1859	$35.19	$35.20	$35.20
Purchase #5	$146.77	10.577%	$162.2939	$162.29	$162.30	$162.30
Purchase #6	$41.94	9.210%	$45.8027	$45.80	$45.80	$45.80
Purchase #7	$150.37	11.701%	$167.9648	$167.96	$167.95	$168.00
7 purchase totals =	$603.92		$668.4588	$668.45	$668.45	$668.50