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	$178.39	8.754%	$194.0063	$194.01	$194.00	$194.00
Purchase #2	$89.54	5.752%	$94.6903	$94.69	$94.70	$94.70
Purchase #3	$147.79	6.158%	$156.8909	$156.89	$156.90	$156.90
Purchase #4	$22.98	10.600%	$25.4159	$25.42	$25.40	$25.40
Purchase #5	$58.27	11.322%	$64.8673	$64.87	$64.85	$64.90
Purchase #6	$72.95	12.607%	$82.1468	$82.15	$82.15	$82.10
Purchase #7	$235.83	10.455%	$260.486	$260.49	$260.50	$260.50
7 purchase totals =	$805.75		$878.5035	$878.52	$878.50	$878.50