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	$139.29	13.498%	$158.0914	$158.09	$158.10	$158.10
Purchase #2	$193.84	3.299%	$200.2348	$200.23	$200.25	$200.20
Purchase #3	$87.88	8.231%	$95.1134	$95.11	$95.10	$95.10
Purchase #4	$160.85	6.490%	$171.2892	$171.29	$171.30	$171.30
Purchase #5	$49.48	6.381%	$52.6373	$52.64	$52.65	$52.60
Purchase #6	$152.96	3.746%	$158.6899	$158.69	$158.70	$158.70
Purchase #7	$178.30	10.209%	$196.5026	$196.50	$196.50	$196.50
7 purchase totals =	$962.60		$1,032.5586	$1,032.55	$1,032.60	$1,032.50