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	$235.66	4.325%	$245.8523	$245.85	$245.85	$245.90
Purchase #2	$211.44	7.111%	$226.4755	$226.48	$226.50	$226.50
Purchase #3	$76.66	11.474%	$85.456	$85.46	$85.45	$85.50
Purchase #4	$33.99	3.239%	$35.0909	$35.09	$35.10	$35.10
Purchase #5	$145.80	13.582%	$165.6026	$165.60	$165.60	$165.60
Purchase #6	$164.62	6.268%	$174.9384	$174.94	$174.95	$174.90
Purchase #7	$143.56	6.236%	$152.5124	$152.51	$152.50	$152.50
7 purchase totals =	$1,011.73		$1,085.9281	$1,085.93	$1,085.95	$1,086.00