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	$72.40	5.119%	$76.1062	$76.11	$76.10	$76.10
Purchase #2	$223.88	13.787%	$254.7463	$254.75	$254.75	$254.70
Purchase #3	$82.73	9.442%	$90.5414	$90.54	$90.55	$90.50
Purchase #4	$127.37	8.749%	$138.5136	$138.51	$138.50	$138.50
Purchase #5	$250.59	8.454%	$271.7749	$271.77	$271.75	$271.80
Purchase #6	$244.96	4.342%	$255.5962	$255.60	$255.60	$255.60
Purchase #7	$37.69	11.151%	$41.8928	$41.89	$41.90	$41.90
7 purchase totals =	$1,039.62		$1,129.1714	$1,129.17	$1,129.15	$1,129.10