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	$41.43	5.610%	$43.7542	$43.75	$43.75	$43.80
Purchase #2	$146.42	12.791%	$165.1486	$165.15	$165.15	$165.10
Purchase #3	$240.51	9.772%	$264.0126	$264.01	$264.00	$264.00
Purchase #4	$93.62	12.442%	$105.2682	$105.27	$105.25	$105.30
Purchase #5	$50.92	6.807%	$54.3861	$54.39	$54.40	$54.40
Purchase #6	$62.81	4.532%	$65.6565	$65.66	$65.65	$65.70
Purchase #7	$242.69	5.270%	$255.4798	$255.48	$255.50	$255.50
7 purchase totals =	$878.40		$953.7060	$953.71	$953.70	$953.80