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	$41.25	7.326%	$44.272	$44.27	$44.25	$44.30
Purchase #2	$206.73	9.524%	$226.419	$226.42	$226.40	$226.40
Purchase #3	$227.78	4.590%	$238.2351	$238.24	$238.25	$238.20
Purchase #4	$125.65	11.326%	$139.8811	$139.88	$139.90	$139.90
Purchase #5	$196.81	9.873%	$216.2411	$216.24	$216.25	$216.20
Purchase #6	$70.88	11.318%	$78.9022	$78.90	$78.90	$78.90
Purchase #7	$191.92	8.592%	$208.4098	$208.41	$208.40	$208.40
7 purchase totals =	$1,061.02		$1,152.3603	$1,152.36	$1,152.35	$1,152.30