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	$242.97	6.269%	$258.2018	$258.20	$258.20	$258.20
Purchase #2	$237.87	5.244%	$250.3439	$250.34	$250.35	$250.30
Purchase #3	$206.59	6.473%	$219.9626	$219.96	$219.95	$220.00
Purchase #4	$85.83	5.224%	$90.3138	$90.31	$90.30	$90.30
Purchase #5	$46.71	4.689%	$48.9002	$48.90	$48.90	$48.90
Purchase #6	$109.57	5.611%	$115.718	$115.72	$115.70	$115.70
Purchase #7	$100.27	13.210%	$113.5157	$113.52	$113.50	$113.50
7 purchase totals =	$1,029.81		$1,096.9560	$1,096.95	$1,096.90	$1,096.90