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	$246.50	9.502%	$269.9224	$269.92	$269.90	$269.90
Purchase #2	$186.88	12.767%	$210.739	$210.74	$210.75	$210.70
Purchase #3	$98.95	6.439%	$105.3214	$105.32	$105.30	$105.30
Purchase #4	$105.48	3.556%	$109.2309	$109.23	$109.25	$109.20
Purchase #5	$145.40	4.299%	$151.6507	$151.65	$151.65	$151.70
Purchase #6	$93.74	12.419%	$105.3816	$105.38	$105.40	$105.40
Purchase #7	$127.86	5.454%	$134.8335	$134.83	$134.85	$134.80
7 purchase totals =	$1,004.81		$1,087.0795	$1,087.07	$1,087.10	$1,087.00