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	$81.47	11.578%	$90.9026	$90.90	$90.90	$90.90
Purchase #2	$107.94	11.637%	$120.501	$120.50	$120.50	$120.50
Purchase #3	$238.67	10.324%	$263.3103	$263.31	$263.30	$263.30
Purchase #4	$132.67	11.458%	$147.8713	$147.87	$147.85	$147.90
Purchase #5	$226.51	4.264%	$236.1684	$236.17	$236.15	$236.20
Purchase #6	$147.85	11.264%	$164.5038	$164.50	$164.50	$164.50
Purchase #7	$27.64	10.738%	$30.608	$30.61	$30.60	$30.60
7 purchase totals =	$962.75		$1,053.8654	$1,053.86	$1,053.80	$1,053.90