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	$52.71	13.315%	$59.7283	$59.73	$59.75	$59.70
Purchase #2	$109.50	3.243%	$113.0511	$113.05	$113.05	$113.10
Purchase #3	$186.54	12.514%	$209.8836	$209.88	$209.90	$209.90
Purchase #4	$209.69	11.441%	$233.6806	$233.68	$233.70	$233.70
Purchase #5	$185.85	3.803%	$192.9179	$192.92	$192.90	$192.90
Purchase #6	$221.62	11.210%	$246.4636	$246.46	$246.45	$246.50
Purchase #7	$82.71	5.713%	$87.4352	$87.44	$87.45	$87.40
7 purchase totals =	$1,048.62		$1,143.1603	$1,143.16	$1,143.20	$1,143.20