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	$67.45	7.561%	$72.5499	$72.55	$72.55	$72.50
Purchase #2	$124.86	10.784%	$138.3249	$138.32	$138.30	$138.30
Purchase #3	$53.40	3.869%	$55.466	$55.47	$55.45	$55.50
Purchase #4	$137.58	13.507%	$156.1629	$156.16	$156.15	$156.20
Purchase #5	$82.95	13.762%	$94.3656	$94.37	$94.35	$94.40
Purchase #6	$98.85	6.194%	$104.9728	$104.97	$104.95	$105.00
Purchase #7	$27.78	12.293%	$31.195	$31.20	$31.20	$31.20
7 purchase totals =	$592.87		$653.0371	$653.04	$652.95	$653.10