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	$224.38	7.814%	$241.9131	$241.91	$241.90	$241.90
Purchase #2	$28.33	9.775%	$31.0993	$31.10	$31.10	$31.10
Purchase #3	$44.67	4.269%	$46.577	$46.58	$46.60	$46.60
Purchase #4	$6.99	12.326%	$7.8516	$7.85	$7.85	$7.90
Purchase #5	$96.27	3.258%	$99.4065	$99.41	$99.40	$99.40
Purchase #6	$193.52	5.870%	$204.8796	$204.88	$204.90	$204.90
Purchase #7	$143.91	5.291%	$151.5243	$151.52	$151.50	$151.50
7 purchase totals =	$738.07		$783.2514	$783.25	$783.25	$783.30