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	$145.27	5.373%	$153.0754	$153.08	$153.10	$153.10
Purchase #2	$150.50	9.167%	$164.2963	$164.30	$164.30	$164.30
Purchase #3	$85.50	11.798%	$95.5873	$95.59	$95.60	$95.60
Purchase #4	$69.90	8.465%	$75.817	$75.82	$75.80	$75.80
Purchase #5	$91.32	7.195%	$97.8905	$97.89	$97.90	$97.90
Purchase #6	$61.39	9.867%	$67.4474	$67.45	$67.45	$67.40
Purchase #7	$62.97	10.679%	$69.6946	$69.69	$69.70	$69.70
7 purchase totals =	$666.85		$723.8085	$723.82	$723.85	$723.80