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	$188.34	13.148%	$213.1029	$213.10	$213.10	$213.10
Purchase #2	$63.69	9.690%	$69.8616	$69.86	$69.85	$69.90
Purchase #3	$12.49	8.214%	$13.5159	$13.52	$13.50	$13.50
Purchase #4	$138.47	7.127%	$148.3388	$148.34	$148.35	$148.30
Purchase #5	$95.90	7.811%	$103.3907	$103.39	$103.40	$103.40
Purchase #6	$186.62	5.312%	$196.5333	$196.53	$196.55	$196.50
Purchase #7	$244.81	3.111%	$252.426	$252.43	$252.45	$252.40
7 purchase totals =	$930.32		$997.1692	$997.17	$997.20	$997.10