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	$114.93	11.190%	$127.7907	$127.79	$127.80	$127.80
Purchase #2	$89.97	12.135%	$100.8879	$100.89	$100.90	$100.90
Purchase #3	$154.74	10.358%	$170.768	$170.77	$170.75	$170.80
Purchase #4	$82.66	9.307%	$90.3532	$90.35	$90.35	$90.40
Purchase #5	$203.33	5.622%	$214.7612	$214.76	$214.75	$214.80
Purchase #6	$220.68	8.122%	$238.6036	$238.60	$238.60	$238.60
Purchase #7	$200.59	11.414%	$223.4853	$223.49	$223.50	$223.50
7 purchase totals =	$1,066.90		$1,166.6499	$1,166.65	$1,166.65	$1,166.80