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	$103.62	8.529%	$112.4577	$112.46	$112.45	$112.50
Purchase #2	$25.93	7.407%	$27.8506	$27.85	$27.85	$27.90
Purchase #3	$156.87	9.780%	$172.2119	$172.21	$172.20	$172.20
Purchase #4	$150.35	12.644%	$169.3603	$169.36	$169.35	$169.40
Purchase #5	$67.56	5.853%	$71.5143	$71.51	$71.50	$71.50
Purchase #6	$211.86	4.435%	$221.256	$221.26	$221.25	$221.30
Purchase #7	$190.70	11.837%	$213.2732	$213.27	$213.25	$213.30
7 purchase totals =	$906.89		$987.9240	$987.92	$987.85	$988.10