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	$59.87	8.603%	$65.0206	$65.02	$65.00	$65.00
Purchase #2	$112.86	3.270%	$116.5505	$116.55	$116.55	$116.60
Purchase #3	$165.36	4.338%	$172.5333	$172.53	$172.55	$172.50
Purchase #4	$163.39	3.303%	$168.7868	$168.79	$168.80	$168.80
Purchase #5	$49.51	9.839%	$54.3813	$54.38	$54.40	$54.40
Purchase #6	$124.69	9.494%	$136.5281	$136.53	$136.55	$136.50
Purchase #7	$181.38	6.231%	$192.6818	$192.68	$192.70	$192.70
7 purchase totals =	$857.06		$906.4824	$906.48	$906.55	$906.50