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	$76.44	13.193%	$86.5247	$86.52	$86.50	$86.50
Purchase #2	$239.95	10.517%	$265.1855	$265.19	$265.20	$265.20
Purchase #3	$241.89	6.144%	$256.7517	$256.75	$256.75	$256.80
Purchase #4	$209.29	6.229%	$222.3267	$222.33	$222.35	$222.30
Purchase #5	$247.50	4.839%	$259.4765	$259.48	$259.50	$259.50
Purchase #6	$60.77	5.503%	$64.1142	$64.11	$64.10	$64.10
Purchase #7	$97.79	3.253%	$100.9711	$100.97	$100.95	$101.00
7 purchase totals =	$1,173.63		$1,255.3504	$1,255.35	$1,255.35	$1,255.40