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	$240.57	9.761%	$264.052	$264.05	$264.05	$264.10
Purchase #2	$130.77	8.236%	$141.5402	$141.54	$141.55	$141.50
Purchase #3	$186.54	8.532%	$202.4556	$202.46	$202.45	$202.50
Purchase #4	$84.86	6.768%	$90.6033	$90.60	$90.60	$90.60
Purchase #5	$125.79	8.359%	$136.3048	$136.30	$136.30	$136.30
Purchase #6	$31.85	5.514%	$33.6062	$33.61	$33.60	$33.60
Purchase #7	$45.31	6.680%	$48.3367	$48.34	$48.35	$48.30
7 purchase totals =	$845.69		$916.8988	$916.90	$916.90	$916.90