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	$102.38	3.597%	$106.0626	$106.06	$106.05	$106.10
Purchase #2	$95.70	5.149%	$100.6276	$100.63	$100.65	$100.60
Purchase #3	$57.46	11.782%	$64.2299	$64.23	$64.25	$64.20
Purchase #4	$238.43	3.793%	$247.4736	$247.47	$247.45	$247.50
Purchase #5	$36.72	3.227%	$37.905	$37.91	$37.90	$37.90
Purchase #6	$73.92	6.688%	$78.8638	$78.86	$78.85	$78.90
Purchase #7	$242.39	11.334%	$269.8625	$269.86	$269.85	$269.90
7 purchase totals =	$847.00		$905.0250	$905.02	$905.00	$905.10