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	$139.46	3.266%	$144.0148	$144.01	$144.00	$144.00
Purchase #2	$184.56	4.206%	$192.3226	$192.32	$192.30	$192.30
Purchase #3	$125.83	6.117%	$133.527	$133.53	$133.55	$133.50
Purchase #4	$96.69	4.301%	$100.8486	$100.85	$100.85	$100.80
Purchase #5	$130.48	9.259%	$142.5611	$142.56	$142.55	$142.60
Purchase #6	$166.76	6.268%	$177.2125	$177.21	$177.20	$177.20
Purchase #7	$52.61	6.649%	$56.108	$56.11	$56.10	$56.10
7 purchase totals =	$896.39		$946.5946	$946.59	$946.55	$946.50