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	$221.34	11.507%	$246.8096	$246.81	$246.80	$246.80
Purchase #2	$77.34	10.372%	$85.3617	$85.36	$85.35	$85.40
Purchase #3	$79.51	6.804%	$84.9199	$84.92	$84.90	$84.90
Purchase #4	$240.50	13.574%	$273.1455	$273.15	$273.15	$273.10
Purchase #5	$59.89	13.293%	$67.8512	$67.85	$67.85	$67.90
Purchase #6	$77.54	7.682%	$83.4966	$83.50	$83.50	$83.50
Purchase #7	$150.49	13.808%	$171.2697	$171.27	$171.25	$171.30
7 purchase totals =	$906.61		$1,012.8542	$1,012.86	$1,012.80	$1,012.90