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	$183.34	4.330%	$191.2786	$191.28	$191.30	$191.30
Purchase #2	$186.95	6.296%	$198.7204	$198.72	$198.70	$198.70
Purchase #3	$171.84	13.320%	$194.7291	$194.73	$194.75	$194.70
Purchase #4	$186.71	4.835%	$195.7374	$195.74	$195.75	$195.70
Purchase #5	$152.35	10.646%	$168.5692	$168.57	$168.55	$168.60
Purchase #6	$77.29	6.111%	$82.0132	$82.01	$82.00	$82.00
Purchase #7	$116.42	6.137%	$123.5647	$123.56	$123.55	$123.60
7 purchase totals =	$1,074.90		$1,154.6126	$1,154.61	$1,154.60	$1,154.60