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	$94.88	4.258%	$98.92	$98.92	$98.90	$98.90
Purchase #2	$155.70	6.661%	$166.0712	$166.07	$166.05	$166.10
Purchase #3	$120.55	9.103%	$131.5237	$131.52	$131.50	$131.50
Purchase #4	$186.94	12.779%	$210.8291	$210.83	$210.85	$210.80
Purchase #5	$115.96	6.322%	$123.291	$123.29	$123.30	$123.30
Purchase #6	$232.90	12.111%	$261.1065	$261.11	$261.10	$261.10
Purchase #7	$111.54	11.110%	$123.9321	$123.93	$123.95	$123.90
7 purchase totals =	$1,018.47		$1,115.6736	$1,115.67	$1,115.65	$1,115.60