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	$84.74	10.205%	$93.3877	$93.39	$93.40	$93.40
Purchase #2	$119.52	11.536%	$133.3078	$133.31	$133.30	$133.30
Purchase #3	$176.78	10.851%	$195.9624	$195.96	$195.95	$196.00
Purchase #4	$138.72	9.803%	$152.3187	$152.32	$152.30	$152.30
Purchase #5	$6.32	3.798%	$6.56	$6.56	$6.55	$6.60
Purchase #6	$28.42	10.357%	$31.3635	$31.36	$31.35	$31.40
Purchase #7	$105.29	5.470%	$111.0494	$111.05	$111.05	$111.00
7 purchase totals =	$659.79		$723.9495	$723.95	$723.90	$724.00