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	$53.40	6.624%	$56.9372	$56.94	$56.95	$56.90
Purchase #2	$54.96	11.447%	$61.2513	$61.25	$61.25	$61.30
Purchase #3	$181.96	5.667%	$192.2717	$192.27	$192.25	$192.30
Purchase #4	$210.61	5.582%	$222.3663	$222.37	$222.35	$222.40
Purchase #5	$23.61	7.298%	$25.3331	$25.33	$25.35	$25.30
Purchase #6	$132.61	7.336%	$142.3383	$142.34	$142.35	$142.30
Purchase #7	$90.53	12.642%	$101.9748	$101.97	$101.95	$102.00
7 purchase totals =	$747.68		$802.4727	$802.47	$802.45	$802.50