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	$105.81	3.354%	$109.3589	$109.36	$109.35	$109.40
Purchase #2	$93.84	6.370%	$99.8176	$99.82	$99.80	$99.80
Purchase #3	$196.90	12.769%	$222.0422	$222.04	$222.05	$222.00
Purchase #4	$174.35	3.456%	$180.3755	$180.38	$180.40	$180.40
Purchase #5	$182.25	5.839%	$192.8916	$192.89	$192.90	$192.90
Purchase #6	$222.42	3.648%	$230.5339	$230.53	$230.55	$230.50
Purchase #7	$207.58	9.806%	$227.9353	$227.94	$227.95	$227.90
7 purchase totals =	$1,183.15		$1,262.9550	$1,262.96	$1,263.00	$1,262.90