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	$227.28	4.758%	$238.094	$238.09	$238.10	$238.10
Purchase #2	$141.48	4.375%	$147.6698	$147.67	$147.65	$147.70
Purchase #3	$78.34	13.112%	$88.6119	$88.61	$88.60	$88.60
Purchase #4	$196.62	11.794%	$219.8094	$219.81	$219.80	$219.80
Purchase #5	$161.45	7.708%	$173.8946	$173.89	$173.90	$173.90
Purchase #6	$169.76	7.142%	$181.8843	$181.88	$181.90	$181.90
Purchase #7	$236.58	9.657%	$259.4265	$259.43	$259.45	$259.40
7 purchase totals =	$1,211.51		$1,309.3905	$1,309.38	$1,309.40	$1,309.40