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	$132.95	10.469%	$146.8685	$146.87	$146.85	$146.90
Purchase #2	$144.82	7.390%	$155.5222	$155.52	$155.50	$155.50
Purchase #3	$168.79	7.432%	$181.3345	$181.33	$181.35	$181.30
Purchase #4	$136.61	4.284%	$142.4624	$142.46	$142.45	$142.50
Purchase #5	$8.72	9.502%	$9.5486	$9.55	$9.55	$9.50
Purchase #6	$188.39	6.642%	$200.9029	$200.90	$200.90	$200.90
Purchase #7	$30.91	7.405%	$33.1989	$33.20	$33.20	$33.20
7 purchase totals =	$811.19		$869.8380	$869.83	$869.80	$869.80