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	$242.86	5.454%	$256.1056	$256.11	$256.10	$256.10
Purchase #2	$12.78	12.111%	$14.3278	$14.33	$14.35	$14.30
Purchase #3	$164.39	13.677%	$186.8736	$186.87	$186.85	$186.90
Purchase #4	$181.38	5.290%	$190.975	$190.98	$191.00	$191.00
Purchase #5	$82.86	10.351%	$91.4368	$91.44	$91.45	$91.40
Purchase #6	$191.36	12.111%	$214.5356	$214.54	$214.55	$214.50
Purchase #7	$78.41	13.380%	$88.9013	$88.90	$88.90	$88.90
7 purchase totals =	$954.04		$1,043.1557	$1,043.17	$1,043.20	$1,043.10