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	$196.29	7.275%	$210.5701	$210.57	$210.55	$210.60
Purchase #2	$186.35	11.689%	$208.1325	$208.13	$208.15	$208.10
Purchase #3	$53.40	10.666%	$59.0956	$59.10	$59.10	$59.10
Purchase #4	$50.78	4.269%	$52.9478	$52.95	$52.95	$52.90
Purchase #5	$180.27	9.648%	$197.6624	$197.66	$197.65	$197.70
Purchase #6	$193.51	10.303%	$213.4473	$213.45	$213.45	$213.40
Purchase #7	$45.79	12.236%	$51.3929	$51.39	$51.40	$51.40
7 purchase totals =	$906.39		$993.2486	$993.25	$993.25	$993.20