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	$148.70	9.106%	$162.2406	$162.24	$162.25	$162.20
Purchase #2	$33.30	3.305%	$34.4006	$34.40	$34.40	$34.40
Purchase #3	$57.55	12.764%	$64.8957	$64.90	$64.90	$64.90
Purchase #4	$107.74	5.237%	$113.3823	$113.38	$113.40	$113.40
Purchase #5	$33.63	10.113%	$37.031	$37.03	$37.05	$37.00
Purchase #6	$126.57	13.677%	$143.881	$143.88	$143.90	$143.90
Purchase #7	$91.65	9.844%	$100.672	$100.67	$100.65	$100.70
7 purchase totals =	$599.14		$656.5032	$656.50	$656.55	$656.50