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	$127.82	11.838%	$142.9513	$142.95	$142.95	$143.00
Purchase #2	$22.56	11.604%	$25.1779	$25.18	$25.20	$25.20
Purchase #3	$142.59	9.794%	$156.5553	$156.56	$156.55	$156.60
Purchase #4	$189.43	8.232%	$205.0239	$205.02	$205.00	$205.00
Purchase #5	$29.39	6.328%	$31.2498	$31.25	$31.25	$31.20
Purchase #6	$130.26	13.148%	$147.3866	$147.39	$147.40	$147.40
Purchase #7	$156.63	3.769%	$162.5334	$162.53	$162.55	$162.50
7 purchase totals =	$798.68		$870.8782	$870.88	$870.90	$870.90