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	$102.47	5.866%	$108.4809	$108.48	$108.50	$108.50
Purchase #2	$33.63	4.136%	$35.0209	$35.02	$35.00	$35.00
Purchase #3	$59.33	7.582%	$63.8284	$63.83	$63.85	$63.80
Purchase #4	$175.69	8.129%	$189.9718	$189.97	$189.95	$190.00
Purchase #5	$129.66	13.686%	$147.4053	$147.41	$147.40	$147.40
Purchase #6	$173.80	9.523%	$190.351	$190.35	$190.35	$190.40
Purchase #7	$180.44	9.113%	$196.8835	$196.88	$196.90	$196.90
7 purchase totals =	$855.02		$931.9418	$931.94	$931.95	$932.00