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	$226.37	9.664%	$248.2464	$248.25	$248.25	$248.20
Purchase #2	$225.97	6.625%	$240.9405	$240.94	$240.95	$240.90
Purchase #3	$228.99	5.469%	$241.5135	$241.51	$241.50	$241.50
Purchase #4	$63.90	13.281%	$72.3866	$72.39	$72.40	$72.40
Purchase #5	$12.81	7.545%	$13.7765	$13.78	$13.80	$13.80
Purchase #6	$71.40	12.603%	$80.3985	$80.40	$80.40	$80.40
Purchase #7	$174.29	3.150%	$179.7801	$179.78	$179.80	$179.80
7 purchase totals =	$1,003.73		$1,077.0421	$1,077.05	$1,077.10	$1,077.00