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	$161.59	4.320%	$168.5707	$168.57	$168.55	$168.60
Purchase #2	$129.57	10.529%	$143.2124	$143.21	$143.20	$143.20
Purchase #3	$226.80	3.121%	$233.8784	$233.88	$233.90	$233.90
Purchase #4	$149.88	3.629%	$155.3191	$155.32	$155.30	$155.30
Purchase #5	$100.53	9.244%	$109.823	$109.82	$109.80	$109.80
Purchase #6	$214.63	4.354%	$223.975	$223.98	$224.00	$224.00
Purchase #7	$19.79	5.474%	$20.8733	$20.87	$20.85	$20.90
7 purchase totals =	$1,002.79		$1,055.6519	$1,055.65	$1,055.60	$1,055.70