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	$184.30	10.644%	$203.9169	$203.92	$203.90	$203.90
Purchase #2	$148.89	8.373%	$161.3566	$161.36	$161.35	$161.40
Purchase #3	$61.76	9.650%	$67.7198	$67.72	$67.70	$67.70
Purchase #4	$55.64	12.470%	$62.5783	$62.58	$62.60	$62.60
Purchase #5	$136.65	12.725%	$154.0387	$154.04	$154.05	$154.00
Purchase #6	$199.27	5.723%	$210.6742	$210.67	$210.65	$210.70
Purchase #7	$181.82	7.871%	$196.1311	$196.13	$196.15	$196.10
7 purchase totals =	$968.33		$1,056.4156	$1,056.42	$1,056.40	$1,056.40