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	$167.46	13.525%	$190.109	$190.11	$190.10	$190.10
Purchase #2	$208.25	4.564%	$217.7545	$217.75	$217.75	$217.80
Purchase #3	$75.48	3.812%	$78.3573	$78.36	$78.35	$78.40
Purchase #4	$18.75	7.630%	$20.1806	$20.18	$20.20	$20.20
Purchase #5	$148.60	10.566%	$164.3011	$164.30	$164.30	$164.30
Purchase #6	$122.86	13.421%	$139.349	$139.35	$139.35	$139.30
Purchase #7	$32.34	4.263%	$33.7187	$33.72	$33.70	$33.70
7 purchase totals =	$773.74		$843.7702	$843.77	$843.75	$843.80