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	$166.64	10.775%	$184.5955	$184.60	$184.60	$184.60
Purchase #2	$23.89	13.650%	$27.151	$27.15	$27.15	$27.20
Purchase #3	$83.38	3.748%	$86.5051	$86.51	$86.50	$86.50
Purchase #4	$75.40	9.647%	$82.6738	$82.67	$82.65	$82.70
Purchase #5	$183.73	4.529%	$192.0511	$192.05	$192.05	$192.10
Purchase #6	$122.47	4.584%	$128.084	$128.08	$128.10	$128.10
Purchase #7	$199.79	11.330%	$222.4262	$222.43	$222.45	$222.40
7 purchase totals =	$855.30		$923.4867	$923.49	$923.50	$923.60