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	$184.89	7.322%	$198.4276	$198.43	$198.45	$198.40
Purchase #2	$69.59	12.203%	$78.0821	$78.08	$78.10	$78.10
Purchase #3	$133.49	5.192%	$140.4208	$140.42	$140.40	$140.40
Purchase #4	$227.57	13.387%	$258.0348	$258.03	$258.05	$258.00
Purchase #5	$219.93	4.529%	$229.8906	$229.89	$229.90	$229.90
Purchase #6	$57.92	12.547%	$65.1872	$65.19	$65.20	$65.20
Purchase #7	$58.37	9.267%	$63.7791	$63.78	$63.80	$63.80
7 purchase totals =	$951.76		$1,033.8222	$1,033.82	$1,033.90	$1,033.80