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	$40.29	9.476%	$44.1079	$44.11	$44.10	$44.10
Purchase #2	$137.97	13.708%	$156.8829	$156.88	$156.90	$156.90
Purchase #3	$152.98	4.520%	$159.8947	$159.89	$159.90	$159.90
Purchase #4	$95.65	4.665%	$100.1121	$100.11	$100.10	$100.10
Purchase #5	$153.55	7.413%	$164.9327	$164.93	$164.95	$164.90
Purchase #6	$162.52	7.339%	$174.4473	$174.45	$174.45	$174.40
Purchase #7	$24.63	3.810%	$25.5684	$25.57	$25.55	$25.60
7 purchase totals =	$767.59		$825.9460	$825.94	$825.95	$825.90