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	$22.85	4.122%	$23.7919	$23.79	$23.80	$23.80
Purchase #2	$199.35	11.723%	$222.7198	$222.72	$222.70	$222.70
Purchase #3	$72.91	7.571%	$78.43	$78.43	$78.45	$78.40
Purchase #4	$55.41	4.436%	$57.868	$57.87	$57.85	$57.90
Purchase #5	$222.64	10.463%	$245.9348	$245.93	$245.95	$245.90
Purchase #6	$13.78	5.166%	$14.4919	$14.49	$14.50	$14.50
Purchase #7	$188.73	10.654%	$208.8373	$208.84	$208.85	$208.80
7 purchase totals =	$775.67		$852.0737	$852.07	$852.10	$852.00