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	$213.67	9.370%	$233.6909	$233.69	$233.70	$233.70
Purchase #2	$75.97	3.520%	$78.6441	$78.64	$78.65	$78.60
Purchase #3	$85.89	12.811%	$96.8934	$96.89	$96.90	$96.90
Purchase #4	$152.84	10.617%	$169.067	$169.07	$169.05	$169.10
Purchase #5	$146.52	4.233%	$152.7222	$152.72	$152.70	$152.70
Purchase #6	$230.84	11.414%	$257.1881	$257.19	$257.20	$257.20
Purchase #7	$96.73	11.527%	$107.8801	$107.88	$107.90	$107.90
7 purchase totals =	$1,002.46		$1,096.0858	$1,096.08	$1,096.10	$1,096.10