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	$32.98	3.267%	$34.0575	$34.06	$34.05	$34.10
Purchase #2	$142.37	5.553%	$150.2758	$150.28	$150.30	$150.30
Purchase #3	$57.90	8.613%	$62.8869	$62.89	$62.90	$62.90
Purchase #4	$65.59	4.311%	$68.4176	$68.42	$68.40	$68.40
Purchase #5	$79.76	3.119%	$82.2477	$82.25	$82.25	$82.20
Purchase #6	$213.39	9.485%	$233.63	$233.63	$233.65	$233.60
Purchase #7	$68.98	3.622%	$71.4785	$71.48	$71.50	$71.50
7 purchase totals =	$660.97		$702.9940	$703.01	$703.05	$703.00