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	$197.73	5.289%	$208.1879	$208.19	$208.20	$208.20
Purchase #2	$55.87	9.769%	$61.3279	$61.33	$61.35	$61.30
Purchase #3	$134.32	4.867%	$140.8574	$140.86	$140.85	$140.90
Purchase #4	$46.93	3.161%	$48.4135	$48.41	$48.40	$48.40
Purchase #5	$95.84	9.411%	$104.8595	$104.86	$104.85	$104.90
Purchase #6	$94.42	5.834%	$99.9285	$99.93	$99.95	$99.90
Purchase #7	$144.45	7.538%	$155.3386	$155.34	$155.35	$155.30
7 purchase totals =	$769.56		$818.9133	$818.92	$818.95	$818.90