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	$40.69	11.759%	$45.4747	$45.47	$45.45	$45.50
Purchase #2	$74.29	5.375%	$78.2831	$78.28	$78.30	$78.30
Purchase #3	$38.98	9.657%	$42.7443	$42.74	$42.75	$42.70
Purchase #4	$230.89	4.698%	$241.7372	$241.74	$241.75	$241.70
Purchase #5	$187.72	13.408%	$212.8895	$212.89	$212.90	$212.90
Purchase #6	$227.94	4.819%	$238.9244	$238.92	$238.90	$238.90
Purchase #7	$66.60	9.463%	$72.9024	$72.90	$72.90	$72.90
7 purchase totals =	$867.11		$932.9556	$932.94	$932.95	$932.90