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	$32.64	3.263%	$33.705	$33.71	$33.70	$33.70
Purchase #2	$179.78	9.344%	$196.5786	$196.58	$196.60	$196.60
Purchase #3	$207.95	11.743%	$232.3696	$232.37	$232.35	$232.40
Purchase #4	$167.52	10.484%	$185.0828	$185.08	$185.10	$185.10
Purchase #5	$136.63	3.524%	$141.4448	$141.44	$141.45	$141.40
Purchase #6	$150.92	7.407%	$162.0986	$162.10	$162.10	$162.10
Purchase #7	$171.63	9.137%	$187.3118	$187.31	$187.30	$187.30
7 purchase totals =	$1,047.07		$1,138.5912	$1,138.59	$1,138.60	$1,138.60