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	$187.54	9.648%	$205.6339	$205.63	$205.65	$205.60
Purchase #2	$197.29	13.503%	$223.9301	$223.93	$223.95	$223.90
Purchase #3	$140.82	9.299%	$153.9149	$153.91	$153.90	$153.90
Purchase #4	$136.31	3.189%	$140.6569	$140.66	$140.65	$140.70
Purchase #5	$179.38	6.687%	$191.3751	$191.38	$191.40	$191.40
Purchase #6	$248.46	10.715%	$275.0825	$275.08	$275.10	$275.10
Purchase #7	$133.74	11.275%	$148.8192	$148.82	$148.80	$148.80
7 purchase totals =	$1,223.54		$1,339.4126	$1,339.41	$1,339.45	$1,339.40