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	$64.55	10.697%	$71.4549	$71.45	$71.45	$71.50
Purchase #2	$76.35	3.263%	$78.8413	$78.84	$78.85	$78.80
Purchase #3	$40.99	9.372%	$44.8316	$44.83	$44.85	$44.80
Purchase #4	$241.65	7.330%	$259.3629	$259.36	$259.35	$259.40
Purchase #5	$142.37	3.523%	$147.3857	$147.39	$147.40	$147.40
Purchase #6	$92.82	12.374%	$104.3055	$104.31	$104.30	$104.30
Purchase #7	$138.53	8.492%	$150.294	$150.29	$150.30	$150.30
7 purchase totals =	$797.26		$856.4759	$856.47	$856.50	$856.50