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	$155.69	7.406%	$167.2204	$167.22	$167.20	$167.20
Purchase #2	$205.67	3.277%	$212.4098	$212.41	$212.40	$212.40
Purchase #3	$188.70	4.111%	$196.4575	$196.46	$196.45	$196.50
Purchase #4	$119.90	9.679%	$131.5051	$131.51	$131.50	$131.50
Purchase #5	$164.44	10.701%	$182.0367	$182.04	$182.05	$182.00
Purchase #6	$36.88	8.398%	$39.9772	$39.98	$40.00	$40.00
Purchase #7	$105.32	5.386%	$110.9925	$110.99	$111.00	$111.00
7 purchase totals =	$976.60		$1,040.5992	$1,040.61	$1,040.60	$1,040.60