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	$52.82	7.707%	$56.8908	$56.89	$56.90	$56.90
Purchase #2	$235.81	5.833%	$249.5648	$249.56	$249.55	$249.60
Purchase #3	$34.44	3.845%	$35.7642	$35.76	$35.75	$35.80
Purchase #4	$213.66	6.187%	$226.8791	$226.88	$226.90	$226.90
Purchase #5	$152.34	13.739%	$173.27	$173.27	$173.25	$173.30
Purchase #6	$116.85	12.128%	$131.0216	$131.02	$131.00	$131.00
Purchase #7	$247.33	8.592%	$268.5806	$268.58	$268.60	$268.60
7 purchase totals =	$1,053.25		$1,141.9711	$1,141.96	$1,141.95	$1,142.10