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	$176.31	4.120%	$183.574	$183.57	$183.55	$183.60
Purchase #2	$42.88	5.252%	$45.1321	$45.13	$45.15	$45.10
Purchase #3	$29.65	13.841%	$33.7539	$33.75	$33.75	$33.80
Purchase #4	$103.52	13.817%	$117.8234	$117.82	$117.80	$117.80
Purchase #5	$138.78	9.597%	$152.0987	$152.10	$152.10	$152.10
Purchase #6	$37.96	5.404%	$40.0114	$40.01	$40.00	$40.00
Purchase #7	$131.82	6.777%	$140.7534	$140.75	$140.75	$140.80
7 purchase totals =	$660.92		$713.1469	$713.13	$713.10	$713.20