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	$199.91	5.237%	$210.3793	$210.38	$210.40	$210.40
Purchase #2	$67.40	7.630%	$72.5426	$72.54	$72.55	$72.50
Purchase #3	$45.48	9.810%	$49.9416	$49.94	$49.95	$49.90
Purchase #4	$178.73	12.454%	$200.989	$200.99	$201.00	$201.00
Purchase #5	$170.62	10.193%	$188.0113	$188.01	$188.00	$188.00
Purchase #6	$173.96	9.447%	$190.394	$190.39	$190.40	$190.40
Purchase #7	$166.79	12.552%	$187.7255	$187.73	$187.75	$187.70
7 purchase totals =	$1,002.89		$1,099.9833	$1,099.98	$1,100.05	$1,099.90