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	$85.57	4.549%	$89.4626	$89.46	$89.45	$89.50
Purchase #2	$216.40	13.865%	$246.4039	$246.40	$246.40	$246.40
Purchase #3	$169.34	4.645%	$177.2058	$177.21	$177.20	$177.20
Purchase #4	$66.73	7.606%	$71.8055	$71.81	$71.80	$71.80
Purchase #5	$156.42	10.566%	$172.9473	$172.95	$172.95	$172.90
Purchase #6	$19.66	10.441%	$21.7127	$21.71	$21.70	$21.70
Purchase #7	$225.71	11.166%	$250.9128	$250.91	$250.90	$250.90
7 purchase totals =	$939.83		$1,030.4506	$1,030.45	$1,030.40	$1,030.40