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	$241.42	4.291%	$251.7793	$251.78	$251.80	$251.80
Purchase #2	$68.70	3.384%	$71.0248	$71.02	$71.00	$71.00
Purchase #3	$102.80	7.451%	$110.4596	$110.46	$110.45	$110.50
Purchase #4	$35.33	8.442%	$38.3126	$38.31	$38.30	$38.30
Purchase #5	$194.69	3.127%	$200.778	$200.78	$200.80	$200.80
Purchase #6	$192.75	3.547%	$199.5868	$199.59	$199.60	$199.60
Purchase #7	$178.47	4.802%	$187.0401	$187.04	$187.05	$187.00
7 purchase totals =	$1,014.16		$1,058.9812	$1,058.98	$1,059.00	$1,059.00