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	$208.51	10.278%	$229.9407	$229.94	$229.95	$229.90
Purchase #2	$216.84	11.850%	$242.5355	$242.54	$242.55	$242.50
Purchase #3	$156.91	6.391%	$166.9381	$166.94	$166.95	$166.90
Purchase #4	$87.91	7.130%	$94.178	$94.18	$94.20	$94.20
Purchase #5	$53.26	11.615%	$59.4461	$59.45	$59.45	$59.40
Purchase #6	$72.85	7.109%	$78.0289	$78.03	$78.05	$78.00
Purchase #7	$199.86	9.511%	$218.8687	$218.87	$218.85	$218.90
7 purchase totals =	$996.14		$1,089.9360	$1,089.95	$1,090.00	$1,089.80