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	$150.80	9.259%	$164.7626	$164.76	$164.75	$164.80
Purchase #2	$12.66	7.334%	$13.5885	$13.59	$13.60	$13.60
Purchase #3	$187.82	8.499%	$203.7828	$203.78	$203.80	$203.80
Purchase #4	$78.58	6.130%	$83.397	$83.40	$83.40	$83.40
Purchase #5	$90.62	8.806%	$98.6	$98.60	$98.60	$98.60
Purchase #6	$86.75	8.425%	$94.0587	$94.06	$94.05	$94.10
Purchase #7	$85.86	5.669%	$90.7274	$90.73	$90.75	$90.70
7 purchase totals =	$693.09		$748.9170	$748.92	$748.95	$749.00