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	$136.34	10.378%	$150.4894	$150.49	$150.50	$150.50
Purchase #2	$97.41	9.337%	$106.5052	$106.51	$106.50	$106.50
Purchase #3	$193.94	4.601%	$202.8632	$202.86	$202.85	$202.90
Purchase #4	$155.47	5.580%	$164.1452	$164.15	$164.15	$164.10
Purchase #5	$30.83	8.616%	$33.4863	$33.49	$33.50	$33.50
Purchase #6	$200.29	6.629%	$213.5672	$213.57	$213.55	$213.60
Purchase #7	$83.88	7.705%	$90.343	$90.34	$90.35	$90.30
7 purchase totals =	$898.16		$961.3995	$961.41	$961.40	$961.40