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	$32.37	6.803%	$34.5721	$34.57	$34.55	$34.60
Purchase #2	$85.65	5.809%	$90.6254	$90.63	$90.65	$90.60
Purchase #3	$106.86	8.771%	$116.2327	$116.23	$116.25	$116.20
Purchase #4	$36.47	11.171%	$40.5441	$40.54	$40.55	$40.50
Purchase #5	$104.44	4.628%	$109.2735	$109.27	$109.25	$109.30
Purchase #6	$144.41	10.790%	$159.9918	$159.99	$160.00	$160.00
Purchase #7	$194.83	9.652%	$213.635	$213.64	$213.65	$213.60
7 purchase totals =	$705.03		$764.8746	$764.87	$764.90	$764.80