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	$144.34	12.793%	$162.8054	$162.81	$162.80	$162.80
Purchase #2	$113.82	3.303%	$117.5795	$117.58	$117.60	$117.60
Purchase #3	$145.76	11.192%	$162.0735	$162.07	$162.05	$162.10
Purchase #4	$165.63	4.442%	$172.9873	$172.99	$173.00	$173.00
Purchase #5	$150.83	13.683%	$171.4681	$171.47	$171.45	$171.50
Purchase #6	$73.83	12.440%	$83.0145	$83.01	$83.00	$83.00
Purchase #7	$163.63	12.732%	$184.4634	$184.46	$184.45	$184.50
7 purchase totals =	$957.84		$1,054.3917	$1,054.39	$1,054.35	$1,054.50