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	$186.84	5.374%	$196.8808	$196.88	$196.90	$196.90
Purchase #2	$228.50	6.200%	$242.667	$242.67	$242.65	$242.70
Purchase #3	$52.70	10.843%	$58.4143	$58.41	$58.40	$58.40
Purchase #4	$105.81	5.466%	$111.5936	$111.59	$111.60	$111.60
Purchase #5	$175.50	11.208%	$195.17	$195.17	$195.15	$195.20
Purchase #6	$233.57	3.339%	$241.3689	$241.37	$241.35	$241.40
Purchase #7	$60.35	6.699%	$64.3928	$64.39	$64.40	$64.40
7 purchase totals =	$1,043.27		$1,110.4874	$1,110.48	$1,110.45	$1,110.60