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	$65.48	10.409%	$72.2958	$72.30	$72.30	$72.30
Purchase #2	$53.82	9.837%	$59.1143	$59.11	$59.10	$59.10
Purchase #3	$109.77	9.663%	$120.3771	$120.38	$120.40	$120.40
Purchase #4	$155.41	5.645%	$164.1829	$164.18	$164.20	$164.20
Purchase #5	$108.61	12.412%	$122.0907	$122.09	$122.10	$122.10
Purchase #6	$148.38	9.159%	$161.9701	$161.97	$161.95	$162.00
Purchase #7	$78.33	10.281%	$86.3831	$86.38	$86.40	$86.40
7 purchase totals =	$719.80		$786.4140	$786.41	$786.45	$786.50