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	$217.47	12.500%	$244.6538	$244.65	$244.65	$244.70
Purchase #2	$126.73	12.410%	$142.4572	$142.46	$142.45	$142.50
Purchase #3	$197.35	11.421%	$219.8893	$219.89	$219.90	$219.90
Purchase #4	$181.25	9.814%	$199.0379	$199.04	$199.05	$199.00
Purchase #5	$155.53	4.334%	$162.2707	$162.27	$162.25	$162.30
Purchase #6	$49.50	10.205%	$54.5515	$54.55	$54.55	$54.60
Purchase #7	$148.96	4.485%	$155.6409	$155.64	$155.65	$155.60
7 purchase totals =	$1,076.79		$1,178.5013	$1,178.50	$1,178.50	$1,178.60