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	$150.27	11.863%	$168.0965	$168.10	$168.10	$168.10
Purchase #2	$231.31	4.368%	$241.4136	$241.41	$241.40	$241.40
Purchase #3	$76.60	12.573%	$86.2309	$86.23	$86.25	$86.20
Purchase #4	$170.98	11.693%	$190.9727	$190.97	$190.95	$191.00
Purchase #5	$33.55	12.846%	$37.8598	$37.86	$37.85	$37.90
Purchase #6	$154.74	5.352%	$163.0217	$163.02	$163.00	$163.00
Purchase #7	$154.36	12.815%	$174.1412	$174.14	$174.15	$174.10
7 purchase totals =	$971.81		$1,061.7364	$1,061.73	$1,061.70	$1,061.70