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	$80.55	12.145%	$90.3328	$90.33	$90.35	$90.30
Purchase #2	$201.25	11.111%	$223.6109	$223.61	$223.60	$223.60
Purchase #3	$124.48	13.515%	$141.3035	$141.30	$141.30	$141.30
Purchase #4	$190.47	11.578%	$212.5226	$212.52	$212.50	$212.50
Purchase #5	$142.54	9.388%	$155.9217	$155.92	$155.90	$155.90
Purchase #6	$52.60	7.211%	$56.393	$56.39	$56.40	$56.40
Purchase #7	$140.34	3.304%	$144.9768	$144.98	$145.00	$145.00
7 purchase totals =	$932.23		$1,025.0613	$1,025.05	$1,025.05	$1,025.00