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	$40.53	7.157%	$43.4307	$43.43	$43.45	$43.40
Purchase #2	$174.28	3.768%	$180.8469	$180.85	$180.85	$180.80
Purchase #3	$82.67	8.288%	$89.5217	$89.52	$89.50	$89.50
Purchase #4	$36.67	9.586%	$40.1852	$40.19	$40.20	$40.20
Purchase #5	$153.43	10.685%	$169.824	$169.82	$169.80	$169.80
Purchase #6	$142.99	11.123%	$158.8948	$158.89	$158.90	$158.90
Purchase #7	$180.67	13.377%	$204.8382	$204.84	$204.85	$204.80
7 purchase totals =	$811.24		$887.5415	$887.54	$887.55	$887.40