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	$38.26	8.112%	$41.3637	$41.36	$41.35	$41.40
Purchase #2	$101.82	7.497%	$109.4534	$109.45	$109.45	$109.50
Purchase #3	$160.34	12.821%	$180.8972	$180.90	$180.90	$180.90
Purchase #4	$32.64	8.871%	$35.5355	$35.54	$35.55	$35.50
Purchase #5	$243.44	11.496%	$271.4259	$271.43	$271.45	$271.40
Purchase #6	$227.97	7.456%	$244.9674	$244.97	$244.95	$245.00
Purchase #7	$54.65	13.185%	$61.8556	$61.86	$61.85	$61.90
7 purchase totals =	$859.12		$945.4987	$945.51	$945.50	$945.60