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	$120.97	3.285%	$124.9439	$124.94	$124.95	$124.90
Purchase #2	$195.90	6.827%	$209.2741	$209.27	$209.25	$209.30
Purchase #3	$10.59	4.329%	$11.0484	$11.05	$11.05	$11.00
Purchase #4	$125.66	13.231%	$142.2861	$142.29	$142.30	$142.30
Purchase #5	$100.54	3.389%	$103.9473	$103.95	$103.95	$103.90
Purchase #6	$168.64	4.724%	$176.6066	$176.61	$176.60	$176.60
Purchase #7	$233.33	12.425%	$262.3213	$262.32	$262.30	$262.30
7 purchase totals =	$955.63		$1,030.4277	$1,030.43	$1,030.40	$1,030.30