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	$236.39	3.337%	$244.2783	$244.28	$244.30	$244.30
Purchase #2	$78.58	8.464%	$85.231	$85.23	$85.25	$85.20
Purchase #3	$226.62	4.363%	$236.5074	$236.51	$236.50	$236.50
Purchase #4	$199.25	8.477%	$216.1404	$216.14	$216.15	$216.10
Purchase #5	$57.30	4.247%	$59.7335	$59.73	$59.75	$59.70
Purchase #6	$153.91	6.720%	$164.2528	$164.25	$164.25	$164.30
Purchase #7	$35.70	11.291%	$39.7309	$39.73	$39.75	$39.70
7 purchase totals =	$987.75		$1,045.8743	$1,045.87	$1,045.95	$1,045.80