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	$218.50	13.740%	$248.5219	$248.52	$248.50	$248.50
Purchase #2	$177.56	4.349%	$185.2821	$185.28	$185.30	$185.30
Purchase #3	$85.69	4.393%	$89.4544	$89.45	$89.45	$89.50
Purchase #4	$29.92	9.659%	$32.81	$32.81	$32.80	$32.80
Purchase #5	$126.95	11.865%	$142.0126	$142.01	$142.00	$142.00
Purchase #6	$171.43	5.346%	$180.5946	$180.59	$180.60	$180.60
Purchase #7	$204.49	7.322%	$219.4628	$219.46	$219.45	$219.50
7 purchase totals =	$1,014.54		$1,098.1384	$1,098.12	$1,098.10	$1,098.20