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	$156.25	10.135%	$172.0859	$172.09	$172.10	$172.10
Purchase #2	$190.46	10.254%	$209.9898	$209.99	$210.00	$210.00
Purchase #3	$87.29	13.683%	$99.2339	$99.23	$99.25	$99.20
Purchase #4	$242.69	9.440%	$265.5999	$265.60	$265.60	$265.60
Purchase #5	$56.78	8.260%	$61.47	$61.47	$61.45	$61.50
Purchase #6	$213.54	11.122%	$237.2899	$237.29	$237.30	$237.30
Purchase #7	$78.45	5.323%	$82.6259	$82.63	$82.65	$82.60
7 purchase totals =	$1,025.46		$1,128.2953	$1,128.30	$1,128.35	$1,128.30