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	$56.48	5.570%	$59.6259	$59.63	$59.65	$59.60
Purchase #2	$194.71	4.477%	$203.4272	$203.43	$203.45	$203.40
Purchase #3	$93.31	6.724%	$99.5842	$99.58	$99.60	$99.60
Purchase #4	$246.59	8.394%	$267.2888	$267.29	$267.30	$267.30
Purchase #5	$80.94	12.220%	$90.8309	$90.83	$90.85	$90.80
Purchase #6	$200.88	3.518%	$207.947	$207.95	$207.95	$207.90
Purchase #7	$10.41	8.816%	$11.3277	$11.33	$11.35	$11.30
7 purchase totals =	$883.32		$940.0317	$940.04	$940.15	$939.90