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	$72.64	10.576%	$80.3224	$80.32	$80.30	$80.30
Purchase #2	$91.95	6.213%	$97.6629	$97.66	$97.65	$97.70
Purchase #3	$104.32	13.314%	$118.2092	$118.21	$118.20	$118.20
Purchase #4	$53.64	10.537%	$59.292	$59.29	$59.30	$59.30
Purchase #5	$213.73	9.277%	$233.5577	$233.56	$233.55	$233.60
Purchase #6	$228.78	5.381%	$241.0907	$241.09	$241.10	$241.10
Purchase #7	$217.94	3.723%	$226.0539	$226.05	$226.05	$226.10
7 purchase totals =	$983.00		$1,056.1888	$1,056.18	$1,056.15	$1,056.30