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	$64.40	12.303%	$72.3231	$72.32	$72.30	$72.30
Purchase #2	$151.48	4.853%	$158.8313	$158.83	$158.85	$158.80
Purchase #3	$150.96	9.180%	$164.8181	$164.82	$164.80	$164.80
Purchase #4	$217.84	7.211%	$233.5484	$233.55	$233.55	$233.50
Purchase #5	$111.91	7.204%	$119.972	$119.97	$119.95	$120.00
Purchase #6	$152.80	12.343%	$171.6601	$171.66	$171.65	$171.70
Purchase #7	$189.85	11.431%	$211.5518	$211.55	$211.55	$211.60
7 purchase totals =	$1,039.24		$1,132.7048	$1,132.70	$1,132.65	$1,132.70