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	$170.86	6.558%	$182.065	$182.07	$182.05	$182.10
Purchase #2	$40.92	3.713%	$42.4394	$42.44	$42.45	$42.40
Purchase #3	$31.52	4.855%	$33.0503	$33.05	$33.05	$33.10
Purchase #4	$74.81	6.185%	$79.437	$79.44	$79.45	$79.40
Purchase #5	$185.99	5.742%	$196.6695	$196.67	$196.65	$196.70
Purchase #6	$61.25	6.725%	$65.3691	$65.37	$65.35	$65.40
Purchase #7	$82.32	4.507%	$86.0302	$86.03	$86.05	$86.00
7 purchase totals =	$647.67		$685.0605	$685.07	$685.05	$685.10