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	$241.90	8.120%	$261.5423	$261.54	$261.55	$261.50
Purchase #2	$141.94	7.681%	$152.8424	$152.84	$152.85	$152.80
Purchase #3	$29.84	10.865%	$33.0821	$33.08	$33.10	$33.10
Purchase #4	$98.62	7.254%	$105.7739	$105.77	$105.75	$105.80
Purchase #5	$136.83	7.353%	$146.8911	$146.89	$146.90	$146.90
Purchase #6	$60.59	3.373%	$62.6337	$62.63	$62.65	$62.60
Purchase #7	$30.46	9.791%	$33.4423	$33.44	$33.45	$33.40
7 purchase totals =	$740.18		$796.2078	$796.19	$796.25	$796.10