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	$30.87	7.508%	$33.1877	$33.19	$33.20	$33.20
Purchase #2	$44.75	7.279%	$48.0074	$48.01	$48.00	$48.00
Purchase #3	$91.48	11.445%	$101.9499	$101.95	$101.95	$101.90
Purchase #4	$156.95	10.803%	$173.9053	$173.91	$173.90	$173.90
Purchase #5	$76.31	3.443%	$78.9374	$78.94	$78.95	$78.90
Purchase #6	$78.65	13.622%	$89.3637	$89.36	$89.35	$89.40
Purchase #7	$90.83	5.247%	$95.5959	$95.60	$95.60	$95.60
7 purchase totals =	$569.84		$620.9473	$620.96	$620.95	$620.90