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	$42.93	8.230%	$46.4631	$46.46	$46.45	$46.50
Purchase #2	$97.80	10.328%	$107.9008	$107.90	$107.90	$107.90
Purchase #3	$62.33	5.761%	$65.9208	$65.92	$65.90	$65.90
Purchase #4	$193.33	10.274%	$213.1927	$213.19	$213.20	$213.20
Purchase #5	$31.61	6.296%	$33.6002	$33.60	$33.60	$33.60
Purchase #6	$34.99	8.391%	$37.926	$37.93	$37.95	$37.90
Purchase #7	$105.40	10.148%	$116.096	$116.10	$116.10	$116.10
7 purchase totals =	$568.39		$621.0996	$621.10	$621.10	$621.10