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	$200.49	9.477%	$219.4904	$219.49	$219.50	$219.50
Purchase #2	$20.56	3.821%	$21.3456	$21.35	$21.35	$21.30
Purchase #3	$171.70	6.502%	$182.8639	$182.86	$182.85	$182.90
Purchase #4	$176.30	13.374%	$199.8784	$199.88	$199.90	$199.90
Purchase #5	$113.42	4.481%	$118.5024	$118.50	$118.50	$118.50
Purchase #6	$53.56	12.823%	$60.428	$60.43	$60.45	$60.40
Purchase #7	$72.80	12.833%	$82.1424	$82.14	$82.15	$82.10
7 purchase totals =	$808.83		$884.6511	$884.65	$884.70	$884.60