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	$71.48	4.731%	$74.8617	$74.86	$74.85	$74.90
Purchase #2	$89.54	13.697%	$101.8043	$101.80	$101.80	$101.80
Purchase #3	$90.82	8.334%	$98.3889	$98.39	$98.40	$98.40
Purchase #4	$46.88	3.464%	$48.5039	$48.50	$48.50	$48.50
Purchase #5	$184.28	6.370%	$196.0186	$196.02	$196.00	$196.00
Purchase #6	$208.30	9.592%	$228.2801	$228.28	$228.30	$228.30
Purchase #7	$118.95	12.693%	$134.0483	$134.05	$134.05	$134.00
7 purchase totals =	$810.25		$881.9058	$881.90	$881.90	$881.90