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	$240.70	11.725%	$268.9221	$268.92	$268.90	$268.90
Purchase #2	$195.39	12.349%	$219.5187	$219.52	$219.50	$219.50
Purchase #3	$104.78	11.197%	$116.5122	$116.51	$116.50	$116.50
Purchase #4	$138.71	6.282%	$147.4238	$147.42	$147.40	$147.40
Purchase #5	$74.86	4.623%	$78.3208	$78.32	$78.30	$78.30
Purchase #6	$52.76	6.465%	$56.1709	$56.17	$56.15	$56.20
Purchase #7	$208.92	7.782%	$225.1782	$225.18	$225.20	$225.20
7 purchase totals =	$1,016.12		$1,112.0467	$1,112.04	$1,111.95	$1,112.00