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	$248.29	5.571%	$262.1222	$262.12	$262.10	$262.10
Purchase #2	$18.47	13.597%	$20.9814	$20.98	$21.00	$21.00
Purchase #3	$34.98	8.431%	$37.9292	$37.93	$37.95	$37.90
Purchase #4	$97.64	13.204%	$110.5324	$110.53	$110.55	$110.50
Purchase #5	$59.89	4.555%	$62.618	$62.62	$62.60	$62.60
Purchase #6	$100.47	11.461%	$111.9849	$111.98	$112.00	$112.00
Purchase #7	$189.42	7.349%	$203.3405	$203.34	$203.35	$203.30
7 purchase totals =	$749.16		$809.5086	$809.50	$809.55	$809.40