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	$75.62	8.783%	$82.2617	$82.26	$82.25	$82.30
Purchase #2	$54.83	4.548%	$57.3237	$57.32	$57.30	$57.30
Purchase #3	$110.91	11.331%	$123.4772	$123.48	$123.50	$123.50
Purchase #4	$194.29	11.874%	$217.36	$217.36	$217.35	$217.40
Purchase #5	$156.78	3.573%	$162.3817	$162.38	$162.40	$162.40
Purchase #6	$157.88	9.601%	$173.0381	$173.04	$173.05	$173.00
Purchase #7	$54.34	8.778%	$59.11	$59.11	$59.10	$59.10
7 purchase totals =	$804.65		$874.9524	$874.95	$874.95	$875.00