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	$179.53	4.182%	$187.0379	$187.04	$187.05	$187.00
Purchase #2	$222.50	12.565%	$250.4571	$250.46	$250.45	$250.50
Purchase #3	$119.38	5.529%	$125.9805	$125.98	$126.00	$126.00
Purchase #4	$125.26	5.584%	$132.2545	$132.25	$132.25	$132.30
Purchase #5	$79.88	4.819%	$83.7294	$83.73	$83.75	$83.70
Purchase #6	$130.93	10.786%	$145.0521	$145.05	$145.05	$145.10
Purchase #7	$79.43	4.421%	$82.9416	$82.94	$82.95	$82.90
7 purchase totals =	$936.91		$1,007.4531	$1,007.45	$1,007.50	$1,007.50