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	$200.47	11.705%	$223.935	$223.94	$223.95	$223.90
Purchase #2	$41.46	11.356%	$46.1682	$46.17	$46.15	$46.20
Purchase #3	$174.84	12.309%	$196.3611	$196.36	$196.35	$196.40
Purchase #4	$92.77	3.526%	$96.0411	$96.04	$96.05	$96.00
Purchase #5	$178.88	11.560%	$199.5585	$199.56	$199.55	$199.60
Purchase #6	$205.45	8.122%	$222.1366	$222.14	$222.15	$222.10
Purchase #7	$249.55	12.176%	$279.9352	$279.94	$279.95	$279.90
7 purchase totals =	$1,143.42		$1,264.1357	$1,264.15	$1,264.15	$1,264.10