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	$115.74	10.471%	$127.8591	$127.86	$127.85	$127.90
Purchase #2	$33.62	6.600%	$35.8389	$35.84	$35.85	$35.80
Purchase #3	$100.96	13.692%	$114.7834	$114.78	$114.80	$114.80
Purchase #4	$181.36	6.780%	$193.6562	$193.66	$193.65	$193.70
Purchase #5	$35.58	4.575%	$37.2078	$37.21	$37.20	$37.20
Purchase #6	$204.33	6.517%	$217.6462	$217.65	$217.65	$217.60
Purchase #7	$150.94	11.481%	$168.2694	$168.27	$168.25	$168.30
7 purchase totals =	$822.53		$895.2610	$895.27	$895.25	$895.30