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	$78.92	9.469%	$86.3929	$86.39	$86.40	$86.40
Purchase #2	$35.97	4.644%	$37.6404	$37.64	$37.65	$37.60
Purchase #3	$102.94	8.490%	$111.6796	$111.68	$111.70	$111.70
Purchase #4	$242.86	7.227%	$260.4115	$260.41	$260.40	$260.40
Purchase #5	$118.43	10.585%	$130.9658	$130.97	$130.95	$131.00
Purchase #6	$61.53	4.646%	$64.3887	$64.39	$64.40	$64.40
Purchase #7	$118.65	7.651%	$127.7279	$127.73	$127.75	$127.70
7 purchase totals =	$759.30		$819.2068	$819.21	$819.25	$819.20