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	$136.60	4.858%	$143.236	$143.24	$143.25	$143.20
Purchase #2	$234.38	10.682%	$259.4165	$259.42	$259.40	$259.40
Purchase #3	$172.43	3.119%	$177.8081	$177.81	$177.80	$177.80
Purchase #4	$39.88	6.791%	$42.5883	$42.59	$42.60	$42.60
Purchase #5	$42.79	8.829%	$46.5679	$46.57	$46.55	$46.60
Purchase #6	$85.30	6.600%	$90.9298	$90.93	$90.95	$90.90
Purchase #7	$107.53	6.652%	$114.6829	$114.68	$114.70	$114.70
7 purchase totals =	$818.91		$875.2295	$875.24	$875.25	$875.20