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	$56.30	13.199%	$63.731	$63.73	$63.75	$63.70
Purchase #2	$78.53	5.169%	$82.5892	$82.59	$82.60	$82.60
Purchase #3	$39.32	9.296%	$42.9752	$42.98	$43.00	$43.00
Purchase #4	$86.78	12.746%	$97.841	$97.84	$97.85	$97.80
Purchase #5	$82.90	5.108%	$87.1345	$87.13	$87.15	$87.10
Purchase #6	$85.34	3.797%	$88.5804	$88.58	$88.60	$88.60
Purchase #7	$11.76	5.243%	$12.3766	$12.38	$12.40	$12.40
7 purchase totals =	$440.93		$475.2279	$475.23	$475.35	$475.20