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	$38.63	12.761%	$43.5596	$43.56	$43.55	$43.60
Purchase #2	$139.66	10.510%	$154.3383	$154.34	$154.35	$154.30
Purchase #3	$175.79	8.236%	$190.2681	$190.27	$190.25	$190.30
Purchase #4	$169.67	8.569%	$184.209	$184.21	$184.20	$184.20
Purchase #5	$99.30	13.605%	$112.8098	$112.81	$112.80	$112.80
Purchase #6	$178.26	10.498%	$196.9737	$196.97	$196.95	$197.00
Purchase #7	$131.98	13.695%	$150.0547	$150.05	$150.05	$150.10
7 purchase totals =	$933.29		$1,032.2132	$1,032.21	$1,032.15	$1,032.30