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	$56.27	8.374%	$60.982	$60.98	$61.00	$61.00
Purchase #2	$201.92	3.298%	$208.5793	$208.58	$208.60	$208.60
Purchase #3	$232.80	13.587%	$264.4305	$264.43	$264.45	$264.40
Purchase #4	$158.54	8.836%	$172.5486	$172.55	$172.55	$172.50
Purchase #5	$100.58	10.568%	$111.2093	$111.21	$111.20	$111.20
Purchase #6	$141.98	7.599%	$152.7691	$152.77	$152.75	$152.80
Purchase #7	$201.69	7.583%	$216.9842	$216.98	$217.00	$217.00
7 purchase totals =	$1,093.78		$1,187.5030	$1,187.50	$1,187.55	$1,187.50