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	$198.95	6.719%	$212.3175	$212.32	$212.30	$212.30
Purchase #2	$55.40	13.855%	$63.0757	$63.08	$63.10	$63.10
Purchase #3	$53.38	7.232%	$57.2404	$57.24	$57.25	$57.20
Purchase #4	$235.67	12.811%	$265.8617	$265.86	$265.85	$265.90
Purchase #5	$134.76	13.472%	$152.9149	$152.91	$152.90	$152.90
Purchase #6	$202.50	13.697%	$230.2364	$230.24	$230.25	$230.20
Purchase #7	$34.68	9.381%	$37.9333	$37.93	$37.95	$37.90
7 purchase totals =	$915.34		$1,019.5799	$1,019.58	$1,019.60	$1,019.50