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	$174.71	9.200%	$190.7833	$190.78	$190.80	$190.80
Purchase #2	$40.69	4.386%	$42.4747	$42.47	$42.45	$42.50
Purchase #3	$172.61	4.182%	$179.8286	$179.83	$179.85	$179.80
Purchase #4	$27.42	7.499%	$29.4762	$29.48	$29.50	$29.50
Purchase #5	$245.91	5.814%	$260.2072	$260.21	$260.20	$260.20
Purchase #6	$249.80	13.214%	$282.8086	$282.81	$282.80	$282.80
Purchase #7	$147.88	8.239%	$160.0638	$160.06	$160.05	$160.10
7 purchase totals =	$1,059.02		$1,145.6424	$1,145.64	$1,145.65	$1,145.70