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	$230.52	10.768%	$255.3424	$255.34	$255.35	$255.30
Purchase #2	$52.75	12.365%	$59.2725	$59.27	$59.25	$59.30
Purchase #3	$181.46	10.787%	$201.0341	$201.03	$201.05	$201.00
Purchase #4	$232.70	13.580%	$264.3007	$264.30	$264.30	$264.30
Purchase #5	$46.64	11.138%	$51.8348	$51.83	$51.85	$51.80
Purchase #6	$125.56	8.650%	$136.4209	$136.42	$136.40	$136.40
Purchase #7	$149.50	11.368%	$166.4952	$166.50	$166.50	$166.50
7 purchase totals =	$1,019.13		$1,134.7006	$1,134.69	$1,134.70	$1,134.60