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	$186.84	5.147%	$196.4567	$196.46	$196.45	$196.50
Purchase #2	$107.94	3.378%	$111.5862	$111.59	$111.60	$111.60
Purchase #3	$128.35	13.791%	$146.0507	$146.05	$146.05	$146.10
Purchase #4	$213.72	12.457%	$240.3431	$240.34	$240.35	$240.30
Purchase #5	$29.55	11.284%	$32.8844	$32.88	$32.90	$32.90
Purchase #6	$110.76	7.133%	$118.6605	$118.66	$118.65	$118.70
Purchase #7	$58.76	8.324%	$63.6512	$63.65	$63.65	$63.70
7 purchase totals =	$835.92		$909.6328	$909.63	$909.65	$909.80