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	$181.86	4.841%	$190.6638	$190.66	$190.65	$190.70
Purchase #2	$97.29	5.735%	$102.8696	$102.87	$102.85	$102.90
Purchase #3	$156.47	7.256%	$167.8235	$167.82	$167.80	$167.80
Purchase #4	$185.32	3.705%	$192.1861	$192.19	$192.20	$192.20
Purchase #5	$205.46	13.823%	$233.8607	$233.86	$233.85	$233.90
Purchase #6	$72.53	5.672%	$76.6439	$76.64	$76.65	$76.60
Purchase #7	$86.78	6.306%	$92.2523	$92.25	$92.25	$92.30
7 purchase totals =	$985.71		$1,056.2999	$1,056.29	$1,056.25	$1,056.40