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	$66.59	9.394%	$72.8455	$72.85	$72.85	$72.80
Purchase #2	$95.87	5.308%	$100.9588	$100.96	$100.95	$101.00
Purchase #3	$246.94	3.383%	$255.294	$255.29	$255.30	$255.30
Purchase #4	$54.40	9.851%	$59.7589	$59.76	$59.75	$59.80
Purchase #5	$207.42	6.248%	$220.3796	$220.38	$220.40	$220.40
Purchase #6	$52.25	9.716%	$57.3266	$57.33	$57.35	$57.30
Purchase #7	$61.44	6.546%	$65.4619	$65.46	$65.45	$65.50
7 purchase totals =	$784.91		$832.0253	$832.03	$832.05	$832.10