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	$93.29	6.801%	$99.6347	$99.63	$99.65	$99.60
Purchase #2	$5.41	8.354%	$5.862	$5.86	$5.85	$5.90
Purchase #3	$25.90	7.585%	$27.8645	$27.86	$27.85	$27.90
Purchase #4	$78.62	8.497%	$85.3003	$85.30	$85.30	$85.30
Purchase #5	$176.92	13.491%	$200.7883	$200.79	$200.80	$200.80
Purchase #6	$145.39	4.541%	$151.9922	$151.99	$152.00	$152.00
Purchase #7	$249.93	6.186%	$265.3907	$265.39	$265.40	$265.40
7 purchase totals =	$775.46		$836.8327	$836.82	$836.85	$836.90