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	$153.93	6.785%	$164.3742	$164.37	$164.35	$164.40
Purchase #2	$223.83	4.421%	$233.7255	$233.73	$233.75	$233.70
Purchase #3	$196.63	8.761%	$213.8568	$213.86	$213.85	$213.90
Purchase #4	$182.43	12.591%	$205.3998	$205.40	$205.40	$205.40
Purchase #5	$213.45	13.395%	$242.0416	$242.04	$242.05	$242.00
Purchase #6	$179.74	5.842%	$190.2404	$190.24	$190.25	$190.20
Purchase #7	$155.50	3.449%	$160.8632	$160.86	$160.85	$160.90
7 purchase totals =	$1,305.51		$1,410.5015	$1,410.50	$1,410.50	$1,410.50