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	$152.62	3.729%	$158.3112	$158.31	$158.30	$158.30
Purchase #2	$37.88	12.169%	$42.4896	$42.49	$42.50	$42.50
Purchase #3	$50.91	8.158%	$55.0632	$55.06	$55.05	$55.10
Purchase #4	$52.33	8.482%	$56.7686	$56.77	$56.75	$56.80
Purchase #5	$65.86	11.493%	$73.4293	$73.43	$73.45	$73.40
Purchase #6	$82.29	3.282%	$84.9908	$84.99	$85.00	$85.00
Purchase #7	$51.74	5.200%	$54.4305	$54.43	$54.45	$54.40
7 purchase totals =	$493.63		$525.4832	$525.48	$525.50	$525.50