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	$211.62	6.839%	$226.0927	$226.09	$226.10	$226.10
Purchase #2	$121.37	10.312%	$133.8857	$133.89	$133.90	$133.90
Purchase #3	$199.25	6.122%	$211.4481	$211.45	$211.45	$211.40
Purchase #4	$133.54	8.375%	$144.724	$144.72	$144.70	$144.70
Purchase #5	$239.79	4.588%	$250.7916	$250.79	$250.80	$250.80
Purchase #6	$26.88	3.661%	$27.8641	$27.86	$27.85	$27.90
Purchase #7	$18.57	11.556%	$20.7159	$20.72	$20.70	$20.70
7 purchase totals =	$951.02		$1,015.5221	$1,015.52	$1,015.50	$1,015.50